MIND ASTE

MEDHA RAJADHYAKSHA

Publications & Information Directorate (CSIR)

Dr K.S. Krishnan MargNew Delhi 110012

India

Mind Master

Medha Rajadhyaksha

© Publications & Information Directorate

First Edition: July 1992Second Edition: November 1993

Third Edition: September 1995rSBN:81-7236-045-2

CSIR Golden Jubilee SeriesPublication No.8Series Editor : Dr. Bal Phondke

Volume Editor: Rajiv Mathur

Cover Design & : Pradip Banerjee, Neeru Sharma, KK Bhatnagar,

Illustrations SushiIa Vohra, AniI Kumar and Malkhan Singh

Production : Radhe Sham, Supriya Gupta, Shiv Kumar andVinod Sharma

Printing : KB. Nagpal, C.M. Sundram,

S. Bhushan, GuIab Singh, S.c. Mamgain,

Rajbir Singh and Gopal Porel

Designed, Printed and Published byPublications & Information Directorate (CSIR)Dr. K.S. Krishnan Marg, New Dethi 110012, India

Price: Rs. 30/-

Foreword

The Council of Scientific & Industrial Research (CSIR), estab­lished in 1942, is committed to the advancement of scientificknowledge, and economic and industrial development of thecountry. Over the years CSIR has created a base for scientificcapability and excellence spanning a wide spectrum of areasenabling it to carry out research and development as well asprovide national standards, testing and certification facilities.It has also been training researchers, popularizing scienceand helping in the inculcation of scientific temper in thecountry.

The CSIR today is a well-knit and action-oriented network of41 laboratories spread throughout the country with activitiesranging from molecular biology to mining, medicinal plantsto mechanical engineering, mathematical modelling tometrology, chemicals to coal and so on.

While discharging its mandate, CSIR has not lost sight of thenecessity to remain at the cutting edge of science in order tobe in a position to acquire and generate expertise in frontierareas of technology. CSIR's contributions to high-tech andemerging areas of science and technology are recognizedamong others for precocious flowering of tissue culturedbamboo, DNA fingerprinting, development of non-noblemetal zeolite catalysts, mining of polymetallic nodules fromthe Indian Ocean bed, building an all-composite light re­search aircraft, high temperature superconductivity, to men­tion only a few.

Being acutely aware that the pace of scientific and technologi­cal development cannot be maintained without a steadyinflux of bright young scientists, CSIR has undertaken avigorous programme of human resource development whichincludes, inter alia, collaborative efforts with the UniversityGrants Commission aimed at nurturing the budding careersof fresh science and technology graduates.

However, all these would not yield the desired results in theabsence of an atmosphere appreciative of advances in science

and technology. If the people at large remain in awe ofscience and consider it as something which is far removedfrom their realms, scientific culture cannot take root.

CSIR has been alive to this problem and has been active intaking science to the people, particularly through the printmedium. It has an active programme aimed at populariza­tion of science, its concepts, achievements and utility, bybringing it to the doorsteps of the masses through both printand electronic media. This is expected to serve a dual pur­pose. First, it would create awareness and interest among theintelligent layman and, secondly, it would help youngstersat the point of choosing an academic career in getting abroad-based knowledge about science in general and itsfrontier areas in particular. Such familiarity would not onlykindle in them deep and abiding interest in matters scientificbut would also be instrumental in helping them to choose thescientific or technological education that is best suited tothem according to their own interests and aptitudes. Therewould be no groping in the dark for them. However, this isone field where enough is never enough.

This was the driving consideration when it was decided tobring out in this 50th anniversary year of CSIR a series ofprofusely illustrated and specially written popularmonographs on a judicious mix of scientific and technologi­cal subjects varying from the outer space to the inner space.Some of the important subjects covered are astronomy,meteorology, oceanography, new materials, immunologyand biotechnology.

It is hoped that this series of monographs would be able towhet the varied appetites of a WIde cross-section of the targetreadership and spur them on to gathering further knowledgeon the subjects of their choice and liking. An exciting sojournthrough the wonderland of science, we hope, awaits thereader. We can only wish him Bon voyage and say, happyhunting.

Preface

We call ourselves "the wise" species, the Homo sapiens. En­dowed with this awareness of special wisdom, there areseveral questions that haunt us. Why we behave the way wedo is one of them. The origin of our rational and irrationalbehaviour looms large as an ever so important conundrum.The complex somatosensory experiences which consolidateas memory and learning in individuals and finally knit intocomplex socio-political structures are hard to understand.With little scope'for experimental analysis, we have searchedfor physical and chemical answers to these questions. Andsome answers we do have. An integral part of each of us, aswe go about our business of living, constitutes the morefascinating aspect of neurobiology. This book tries to presentsome of these exciting developments.

Evolutionary forces have blatantly favoured a skilled sen­sorium, our brain. Perceptions have attained finesse as neverbefore. In addition, there are neuronal qualities that are ex­clusively human and have given us an edge over the rest ofthe living world. Our ability to learn, to remember, to imagineand to create has been our strength. Speaking up - to beheard not only in a life time but also for generations to comeis what has made our species a successful one. This bookhighlights these special skills we have.

In an exposition on Vedanta, Swami Vivekananda pointsout "There is really no difference between Matter, Mind andSpirit". Neurobiologists today tend to agree, though for dif­ferent reasons. But this grey matter that expresses itself asmind does not reveal its secrets easily. To date what we knowis because of contributions that have emanated from all the

fields of science. Recently biologists have formed a nexuswith computer scientists that has proved fruitful. This booktraces some developments in our process of knowing oursel­ves albeit a little sketchily. The brevity of the book may proveto be its strength, as all that is unsaid might act as a stimulusto reach out for more serious text. But the basic objective is tokindle an interest in neurobiology. The book seeks to dojust that.

Acknowledgement

They say dreams don't come true. This one did, as Dr. G.P.

Phondk.e was k.ind enough to give me an opportunity to writefor the CSIR Golden Jubilee Series. Offering timely en­couragement to all my academic endeavours, Dr. Phondkehas been an inspiring teacher. I thank. him for his lessons inpopular science writing and specially for guiding me makethe text of this book presentable.

The source of strength that helped me tide over thebeginner's blues has been my husband, Shailesh. Substitut­ing him for a casual reader, I have forced him to taste all my'literary delights'. I would not have written at all but for hisunwavering support.

My sister Pradnya and her husband, Dr. Satish Gaitonde,read carefully through the text and offered valuable sugges­tions. Very special thanks to them.

A lot of time could be spent on the book because of thesupport of elders in the family. The critical comments frommy parents and encouragement from my mother-in-lawhave helped all the way. A word of thanks to them.

Loving thanks to my children Gauresh and Meghna forbearing with me and for learning to be on their own as I wroteto meet the deadline.

The help rendered by Mr. George D'Souza is greatlyacknowledged-his typing skills helped out in the tightschedule.

Medha Rajadhyaksha

To

my teachers and my ,tudent,

who have always been

a louree of in'piration

-Medha

('ontents

The Head Quarters

Network of Cells

The Grey Terrain

Learning Times

Breaking the Silence

Memory Musings

The Brightness Marked

A Creative Chemistry

Not Yet the Last Word

Glossary

... 1

... 12

... 30

... 43

... 55

... 70

... 80

... 92

...105

....108

TheHead

Quarters

TANDING beneath a starlit

sky, gazing at the twinklingwonders above, one is struck

by a sense of awe. A feeling ofoneness with the void above ismixed with the realization of theinsignificance of human life. Thefleeting timelessness experiencedsharply focuses the limits of ourown life spans. These thoughtsthat cross our mind sometime or

the other are probably unique toour species. We seem to be theonly ones living through a stretchof time, knowing well in advancethat it is limited. The knowledge,that death is predestined and isthe ultimate truth, is probably notshared with other living beingson earth. That surely makes usspecial. The fact that we are nothere for ever maKes us seek

within ourselves and beyond apurpose for our individual life. Anew dimension is added to meresurvival! And one wonders

whether it is this insight that hasmade us what we are today. Eachone of us is a thinker,philosopher, explorer, learnerand teacher, in one's own smallway, learning from the agesbegone - like no other livingform can - endowed with a spe­cial form of communication thatbreaks the barriers of time and

language. Such unique faculties

2 MIND MASTER

Each one of us is a thinker, philosopher, explorer,learner and teacher, in one's own small way

THE HEAD QUARTERS 3

have been acquired through the painfully prolonged processof evolution. Their emergence is a miracle in itself!

Strategies for survival of life on earth are diverse and avariety of sizes, shapes, life styles have developed. Most ofthe life forms find a silent niche for themselves - slowlyadapting to an ever changing environment. The unpre­dictable harshness of the surroundings often take the toll ­strategies fail, leading to extinctions. With the arrival of Homosapiens a new strategy is at test! Life is more than a matter ofchance - it is a conscious effort. Environment that cannot be

adapted to can be purposefully changed - if not totally,substantially.

And these impositions on our surroundings have in turnevolved us continuously! With time, human colour, stature,size and form seem to play less of a role for survival. Thevaried functions of our brain, its plasticity and adaptabilityappears to offer an edge over other forms of life on earth. Ournervous system has come a long way - still carrying func­tional relics of our remote past. We have it all within us ­nerve nets as simple as that of primitive organisms likeHydra, 'ganglionic' collection of neurons like that of inver­tebrates, brain stem like that of early vertebrates and ofcourse a little more! The fundamental unit has remained the

same throughout the march of evolution. An assemblage of'neurons'. What has changed is the outlay - the map of thisneuronal assembly. Functional concentration of these cellularunits, the neurons, has made up the structure we call thebrain. The brain has turned out to be the most versatile organin our evolutionary process - ever changing. Over theepochs some functions have been added, some have beendeleted, some have amplified, while others have declined.Changes have taken gross anatomical forms or have beensubtle chemical ones. And here we are today, with a map ofthe brain, fairly exclusive but with a lot in common with allothers before us!

4 MIND MASTER

. Evolutionary tree

THE HEAD QUARTERS

Hydra

Segmental

ganglion

Earthwonn

5

The human nervous system retains characteristics of thatof its evolutionary ancestors

In very early vertebrates when the fundamental blue printof the brain was laid it was a very simple one - the 'forebrain' to receive information about how the surroundingssmell, the 'mid brain' to help 'see' and the 'hind brain' toperceive sound. In addition, the hind brain also helped inbalancing and kept an eye on the parts of the animal that filledthe body cavity. The signals from the sensory sources werebrought in through the spinal cord or just directly into thebrain. Bundles of nerves bringing in the signals organizedthemselves as 'sensory tracts' while other bundles that car­ried signals back as a response to the stimuli formed the'motor tracts'. Inevitably, a majority of motor tracts ultimate­ly ran into muscles. Where the sensory and motor pathways

\

6 MIND MASTER

Hind brain

~

The premitive vertebrate brain

met, a specific organizational unit of the brain played a rolefor their integration. The mid brain emerged as the major siteof this liaison. As vertebrates evolved, complexities wereadded to this basic layout. The three major parts of the brain- fore brain, mid brain and hind brain were functionally and

structurally enriched to variable extents. The present ver­satile brain we have is a net result of some of these over­

whelming modifications.

Weighing about 1,300 grams, we have a brain far bigger insize than that expected of a mammal of our weight. The jellylike dirty grey matter that forms more than three quarters of

THE HEAD QUARTERS

It""G ----

50

60

0.1

60

'5000

~1700

300

100

1450

7

our brain is the cerebrum. Furrowed with deep folds, halvedby a central fissure, the entire layer of the cerebrum forms thepart rich in neuronal cells. This is the' neo cortex' formed fromthe roof of the fore brain of the primitive blue print. It is thispart that makes us different from other animals - it stores ourmemories, records our perceptions and performs the otherspecial functions our brain is endowed with. Both the halves- the hemispheres - of the cerebrum are the store houses ofall that we have learned. Our skills, oral and muscular, areengraved in this part. Areas that help us hear, see, speak,remember and perform delicate muscle movements can bemapped in the grey mass. The two halves of the cerebrumthough asymmetrical and independent are in league witheach other. They exchange notes and share information con­tinuously through millions of nerve tracts which cross

8 MIND MASTER

overfrom either side - called 'the corpus callosum' and 'theanterior commisure'. Also deep inside is an aggregate ofneuronal cells - 'the basal ganglia' - the part that helps ingross body movement.

The cerebral office, performing the ever so important func­tions need to be supplied with information continuously. Theinputs need to be sorted and reported to the appropriate sub­region. This task isdon~by 'the thalamus'. Fused to the baseof the cerebrum, the thalamus relays signals coming up fromthe brain stem and spinal cord. The thalamus has a partner,the hypothalamus. Modest in size, the hypothalamus is verymuch in control of the internal body functions. Its ability toconduct the orchestra of hormones by sending forth 'releas­ing factors' is impressive. For the cerebral functions to be

THE HEAD QUARTERS 9

appropriately ex- I

ecuted the fine tuningof the body byhypothalamicmod ulation of hor­

mones is imperative!With all our so

called 'higher func­tions' in full swing, weat times land up beinga bundle of nerves.Emotions overtake all

other aspects of per­ceptions. A complexchurning of memories,emotions and percep- Itions makes us behave Thetwo hemispheres

as we do. Amygdala,together with hypothalam us is responsible for mixing' emo"tions with perceptions and memories. The amygdalaalongwith hippocampus forms the 'limbic system' - aregion that helps store memories for long time. The borderingareas of the fore brain constitute the limbic system whichseparates the regions that performs more 'human function'from those that perform fundamental 'animal functions'.This region performing the very basic functions is the brainstem - evolved from the mid brain and the hind brain of the

primitive vertebrate brain. Nerve tracts run through the stemupto the thalamus. Signals to muscles for performing everymundane function of the body run down to the spinal cordthrough the brain stem. Centres for controlling movement ofour eye muscles and for craning the neck or totally turningaround are lodged in special pools of neurons in the 'midbrain' and 'the pons' and are laid out within as a network ofcells knpwn as 'reticular formation'. Part of this cell poolgoverns our stature and posture. The co-ordinator of a

10

Limbic system

MIND MASTER

Neocortex

Three levels of brain

majority of our responses is the cerebellum. Our erect, agilewalk, our equilibrium, the subtle phasing of our movementsas required for certain actions - all the physical charac­teristics that have helped us evolve are supplied by the brainstem. Running down from the brain and secured within thebony vertebral column is the spinal cord - the extension thatat times performs on its own.

No better anatomical architectural plan seems possiblethan the one we have acquired through the ages. Trulydemocratic, each part of the brain has its say - none can besaid to be more important than the other. Co-operation,co-ordination and co-existence is the theme - successful

survival and creativity has been the result!

Travelling through the terrain of our brain is as exciting asastral travel and is in no way simple! Our limitations areobvious. As David H. HUBEL(1926-), the neurobiologistfrom Harvard puts it - "Can a brain understand the brain?"

THE HEAD QUARTERS 11

"Can a brain understand the brain?"

With aH our modest means we have made some commen­

dable attempts! The mazes of the brain have been enteredthrough several doors. Studies have been carried out atvarious levels. At the anatomical level - well within the

reach of the resolution of our eyes. At the cellular level- thelevel introduced by Antonj van LEEUWENHOEK (1632­1723) with the discovery of the microscope. At the molecularlevel- the frontiers which we tread at present! At each ofthese levels of organization, pieces of jigsaw are formed ­some meaningful, others yet waiting to fit into a picture.Together they bring forth a hazy story of how we are manag­ing to run our body functions smoothly, like any otheranimal. In addition we are able to do a little more - learn,

remember, speak, think and judge.

Networkof

Cells

HAPED like tiny stars withlong tails, neurons, the spe­cialized cells of the nervous

system, are organized to form thebrain. Almost equal to the num­ber of stars in our galaxy, thehuman brain is thought to be

11made up of no less than 10 ,thatis one hundred thousand millionneurons - each a little different,yet having an identical set of basiccharacters. Each had a body withseveral arms known as thedendrites. In addition is a long tail- axon that reaches out to other

cells. Coming in a variety of varia­tions of the same theme, thesecells are functionally remarkably.versatile. Holding them in softpackings, helping them functionas they do are the set of accessorycells the 'glial cells'. For yearsthese building blocks of the brainremained beyond the reach ofcytologists, more so because oftheir peculiar shape that spannedseveral layers of the tissue. Theyear 1875 brought a breakthrough. The Italian histologistCamillio GOLGI (1843-1926)devised a method for stainingsingle neuron. The Golgi techni­que was exploited to its maxi­mum by Santiago Ramon yCA] AL (1852-1934) who virtuallystudied every part of the nervoussystem. The Nobel Prize was

NETWORK OF CELLS 13

shared by these two con­temporary stalwarts in1906 for pinning down theelusive neutons.

What makes theneurons so efficient in car­

rying messages is theirspecialized cell mem­brane. The cell membrane

of a neuron is a sea, of lipidwi th some specialproteins floating likeicebergs. Some of theseproteins function likeionic pumps, while others Ilike channels. Still others

are enzymes or receptors. Helping to hold them in a fluiddynamic state are structural proteins also. These proteinsmay function in liaison or independently, ensuring an electri­cally active membrane. A very crucial set of proteins are theones that act as pumps for ensuring an appropriate balanceof sodium and potassium ions inside the cell. This pumpactively expels sodium ions out while pulls potassium ionsin, resulting in an uneven distribution of these ions on eitherside of the neuronal membrane. Adding to this disequi­librium are some channel proteins that selectively allowpotassium ions to leach in but not the sodium ions. In aneuron at rest, if a fine glass electrode is gentl y pushed in, themembrane closes over it, with minimal damage to the cell.With another electrode outside the cell a voltage differencecan be recorded across the membrane. On the negative side,only 70 m V, this voltage difference is, however, substantialas the ceIl membrane is very thin. A small change in thisvoltage, therefore, can bring about radical changes in thepositions and alignment of membrane-linked proteins. Thisis exactly what happens when the membrane is stimulated!

14 MIND MASTER

"

Santiago Ramon y Cajal (right) studied the nervous system using thetechnique devised by Camillio Golgi (left)

NETWORK OF CELLS 15

Activation •Gateopen ••••. --'" ,,---. -...

-- -

Potas;sium'~

.---.,,-------- ",,--,-•• • •••• -: •••• - : •• • lnactivation~ ••• :. - .....• - - •••••••••••• Gate closed•••

J

Outside- _

Axonmembrane

inside _ • -_....~ .• ••I

larue exchange across neuron membrane, proposed by Sir AndrewFielding Huxley (left) and Sir Alan Lloyd Hodgkin (right)

In the year 1952 Sir Alan Lloyd HODGKIN (1914- )and SirAndrew Fielding HUXLEY (1917-) of Cambridge Universitypublished results of a series of experiments that providedmolecular explanation of how a message conveyed to theneuron is passed on. It seems to be like igniting the fuse of acracker - fired neurons transmit messages swiftly. Anamply stimulated neuron, the one that has received a largeenough message, is no longer in its steady, resting state. Theproteins in its membrane are shaken up. The channel proteinsrearrange themselves so as to now permit sodium ions intothe cell. In a mad rush, the sodium ions rush-in as the voltagedifference is abolished. In no time the voltage recordedreaches a positive peak of +30mV.The influx of ions is curbedonly when the channel proteins reorient to shut off the gates.The membrane iimps back to its unstimulated state withpumps draining out sodium ions and reestablishing a nega­tive voltage. In other words, with a controlled interplay ofcurrents and cross currents of ions, and timely opening andclosing of channels, the membrane of the neuron responds to

16 MIND MASTER

The message spreads rapidly by jumping fromone point to another

NETWORK OF CELLS 17

a stimulus by generating a big pulse of electrical activity.Unable to be contained in a part of the cell, this spike ofelectrical disturbance spreads rapidly, across the cell body,along the axon right to the extrimities of the neuron. Themessage is on the run - coded as a frequency of pulses. Toadd to the speed of conduction, the message travels by leap­ing over stretches of axon. These jumps are possible onlybecause the glial cells lend a helping hand! A special glial cell,the Schwann cell, present around the axon, provides stretchesof insulated axonal surfaces. This insulation, the myelinsheath, breaks only at few points ~ the nodes of Ranvier.Jumping from one node of Ranvier to another, the impulsetravels at a commendable speed right to the button shapededge of the cells. It is now a question of transferring informa­tion to another cell.

In the year 1897 an English physiologist Sir Charles ScottSHERRINGTON (1857-1952) proposed the presence of ananatomical junction between neuronal cells - that laterturned out to be the site of extraordinary importance inscreening messages in the brain. Writing a chapter for arevised text book on neurophysiology, Professor Sherringtonfirst introduced the term that represented connectionbetween two neurons - the synapse - derived from Greek.synapsis, meaning to clasp orto connect. An expert in his field,Professor Sherrington further expanded his ideas in hisfamous book - "The Integrative Action of the Nervous System"and explained the functional plasticity of these connectionsin the brain as: "Such a surface might restrain diffusion, bankup osmotic pressure, restrict the mo~ements of ions, accumu­late electric charges, support a double electric layer, alter inshape and surface tension with changes in difference ofpotential ". Synapses have turned out to be junctionswhere tiny but important decisions are made. Each neuronmakes about a thousand synapses with other neurons. Noless than 1015, (one thousand million million) synapses active­ly participate in the hectic transmissions that run the brain.

18 MIND MASTER

Neurons release bags of chemical messangers into the synaptic gap.Inset - Sir Charles Scott Sherrington who coined the word' synapse'

NETWORK OF CELLS t9

At the synapse, the message rushing through the neuronpauses as there is a physical gap between the membranes ofthe two neurons that cannot be bridged. An alternate strategyto cross the void has to be employed. Chemicals known asneurotransmitters rush to help in this endeavour. The mes­sage is carried across by these chemical messengersgenerated by the neurons themselves. The synaptic junctionsthus function as tiny court rooms where chemicaljurisprudence is used; messages arriving from various sour­ces are reviewed before they are transmitted further. Somemessages are sent forth with reenforcement, while otherswith a little toning down while still others not at all! Modifiedto varying degrees, the messages flow through organizedassemblies of neurons acquiring a new meaning at everystage.

The neuronal circuits, the pathways formed by a group ofneurons to carry impulses to their destination, are well estab­lished in the human brain. The association between two

functionally distinct neurons is the simplest form of neuronalcircuit seen in the animal kingdom. The sensory neuron thatbrings in information forms the input component, while themotor neuron that carries the signal to the responding muscleor glands is the output component. In this simple, two com­ponent situation it is obligatory that every input by sensorystimulation is faithfully transmitted on to the motor counter­part, eliciting one appropriate response. However, the situa­tion in the human nervous system is not so simple! The twocomponents, the sensory and the motor, are separated by aset of functionally distinct cells, the 'intermediate neurons',which form a strategic barrier between the input terminusand the output terminus. The impulse travelling through isnow offered an opportunity to catch its breath! An importantelement of decision-making creeps in - messages can eitherbe held back or passed on. In addition, there is scope formodification of the messages. The scene is set for performingcomplex computational functions.

20 MIND MASTER

~-':::-_'~:l! '--

•

Neurotransmitters carry the message across the gap between themembranes of two neurons

NETWORK OF CELLS 21

The input sensory component brings the message at the decisionmaking centre before it is passed on via the output motor component

The 'intermediate network' of neurons makes up 99.98%of the total number of neurons in the human central nervous

system. The truely sensory neurons, in fact, do not form a partof the central nervous system but instead constitute theganglia that flank the brain and the spinal cord. On the otherhand the genuine motor neurons (about two to three million),make up barely a fraction of the vast neuronal net.

This circuitry of the intermediate neurons, spanning themajor part of the brain, is essentially responsible for thebrain's finer qualities. A very important consequence of sucha network is the increased potential for variation. For everyinput, the response can be of many types, and the quality ofresponse would depend largely upon how the information

22 MIND MASTER

sent in is handled by the intermediate set of neuronal cells.Each additional intermediate neuron opens a new possibility- an alternative pathway for transmission. With such largenumbers, the choice available is obviously stupendous! Thisscope for variation is what makes the human brain superiorto computers.

Another fascinating aspect of the neuronal circuitry is itsplasticity which makes neurons more than cables carryingelectrical pulses. Circuits can be made, changed and broken.Discussing 'the ascent of man', Jacob BRONOWSKI (1908­1974) had said "Man is unique not because he does science,and he is unique not because he does art, but because scienceand art equally are expressions of his marvellous plasticityof mind". At the cellular level the 'synapse' is to an extentresponsible for plasticity of a neuronal pathway. The synap­tic functions can be initiated, discontinued or strengthenedas the situation demands and the ability of a neuronal path­way depends on the nature of these synaptic inter-locks. Therich variability and a continuing plasticity endow the net­work of neurons with an unlimited creative potential.

The actual layout of the wiring of the brain is now beingworked out painstakingly by neurobiologists. In general, it iswell known that pools of neuronal cells are arranged in sucha way that a certain pattern of information flow is possible.At times, a single input needs to be shared with many ele­ments for which the signals are required to be sent to variousregions simultaneously. The functional interconnections thatdevelop for such a purpose form a 'divergent circuit'. Startingas the firing of a single neuron the message is able to reach ahundred or more cells. This amplification, makes possible achange in the direction of the impulse. Signals originating ata single point can be relayed through multiple tracts todifferent anatomical sites. On the other hand, informationcoming in from several sources can be consolidated at oneoutput element. Such a 'convergent circuit' ensures a singlereaction to multiple stimulations.

NETWORK OF CELLS 23

"Man is unique not because he does science, and he is unique not be­cause he does art, but because science and art equally are expressions

of his marvellous plasticity of mind"

24 MIND MASTER

The message is carried ahead with everynew neuron roped in

An efficient sequencing of neurons can result in a stimula­tion being sustained for a stretch of time. The input neuroncauses firing of another neuron which in turn not only passesthe stimulation further but sends it back to the first (input)one too. In other words, a sort of feed back takes place. Thetheme is repeated as the pulse is carried ahead and with everynew neuron roped in, the original input neuron fires andstarts the transmission all over again. The pulse echoes backand forth continuously in a 'reverberating circuit' until thecells are exhausted. The reverberation can, of course, becurbed by active inhibition.

Another cellular mosaic for repetitive stimulation is pos­sible without the element of feedback. This form of circuit,known as the 'parallel' one, has an edge over the rever-

NETWORK OF CELLS 25

Gol Gumbad of Bijapur: The pulse echoes back andforth continuously in a reverberating circuit

beratory one as it is not constrained by fatigue of the system.However, many more cells need to participate in forming it.Information runs through several by-lanes and arrives at theoutput neuron not all at once but with short gaps of time. Thenet result is a pulsed output signal for one single input. Thisintricate meshwork leaves one wonder-struck. To think that

all our ingenuity dwells in these cellular arrangements ­these circuits which interweave to perform not only motorfunctions but also the intellectual ones!

Like any other mature association, the relations betweentwo neurons cannot be made or broken at short notice. This

network for intelligence develops, slowly and steadily, intoadulthood. The intellectual development is known to have atimetable of its own, somewhat specific for each of us. JeanPIAGET of Geneva University, has worked out a generalschedule of human intellectual development on the basis ofpsychological tests. According to his study, in the time-spanfrom birth to adulthood, most of us go through five stages ofintellectual development. The first of these stages is when the

child perceives the environmentaround it just as it is. Unable toperform any logical, mentaloperations, this 'sensory-motorperiod' is probably a very excit­ing period of our lives - full ofsimplistic discoveries. The nexttwo years are the one of acquiringlinguistic skills. This periodwhen 'pre-opera tive thoughts'first appear is when the toddlersare chattering monkeys -learn­ing the language at full speed andimitating the adults in almosteverything possible. The agegroup four to seven years is when'intuitive thoughts' are initiated.A little later, at the age of eight toeleven years, a lot of 'common

26 MIND MASTER

The network of intelligence develops, slowlyand gradually, in to adulthood

NETWORK OF CELLS 27

sense' enters the little head. A significant maturation of intel­lectual functions takes place during adolescence. Reason andlogic form the basis of the thought process but abstractionscan be appreciated as well. Hypothetical ideas can be hand­led with ease. As a result the human mind emerges with itsmost refined qualities!

The age at which each of these developmental milestonesare arrived at may vary with individuals, yet essentiallysimilar processes help acquire maturation of the mind. Ateach stage, probably, subtle qualitative changes in the micro­architecture of the brain take place. The neuronal networkacquires definitive expression at different times, in differentparts of the brain. The computational layout of the cerebralcortex probably gets its finer touches as the flair for reasoningand fantasizing develops. What constantly helps the estab­lishmen t of the neuronal circui ts are the genes wi thi n and thesensory inputs from the environment. Timely interactionsbetween the maturing parts of the brain playa critical role.The cellular wiring in the centres of learning of the brain,however, is never complete or permanent. Childhood lingerson, until the very end in the form of synaptic plasticity.

All throughout the development, each brain cell activelyparticipates in finding a niche for itself. Cells reach out send­ing forth several appendages, the dendrites, that impinge onseveral other cells. Axonal fibres stretch over long distancesseeking appropriate contacts. Axon collaterals, the additionalaxonal limbs, sprout and form important segments, especial­ly of the reverberatory circuits. Cellular destinations andspace appear to be fairly predetermined, for very preciselinks appear at specific times during development. Molecularclues probably guide the growing neuronal endings and helpthem initiate synaptic junctions. This 'selectivesynaptogenesis' on the basis of'chemical affinities' was sug­gested by J.N. LANGLEY (1852-1925) as early as in 1895.Though several studies support this idea, it has been difficult

28 MIND MASTER

I I Im""'" II

~-~. fi) ~ .A machine can be studied in two ways either

as a whole or component wise

NETWORK OF CELLS 29

to demonstrate presence of specific molecules that participatein guiding dendritic out-growths.

What we know today, more or less definitely, are theperipheral aspects of the intellectual functions of our brain.On one hand a histological and biochemical profile of thebrain is available, while on the other functional links havebeen mapped. Yet, tracing and establishing how exactly aneural circuit works for a specific intellectual function re­quires something more - something the neurobiologists aregroping for. There is, however, another approach to theproblem - a recent one and a very challenging one!

One way of knowing about a machine is by studying thewhole and then try to determine the role played by each ofthe constituents. An alternative is to assemble an effectivelyrunning system starting from some fundamental units. Thecomputer scientists are working on these lines and are insearch of' artificial intelligence'. Though the' chips' used forthis purpose are not live ones, they share a lot in commonwith the neuronal network. Though exact analogies betweenthe electronic brain and a human one cannot be drawn,programmes that mimic human intellectual functions wouldprobably give clues to the way cells interact while processinginformation.

The GreyTerrain

HE cerebral cortex, the roofof the brain, has a spec­tacular evolutionary his-

tory running almost parallel tothe development of special fea­tures of the human species. Theculmination of evolution result­

ing in free, tool-making, tensilehands, the emergence of speechand process of thinking is closelylinked to the elaboration of a uni­que region of the cerebrum the'new mantle' or the 'neo pallium'.This grey cap is what makes us sodifferent, not only from otherprimates but also from oneanother. Acting as an organiza­tional head of all the other centresof the brain, the cerebral cortexhas critical functions to execute. It

receives signals from the sensorylimbs either directly or after aprocessing has taken place at thesmaller corporations of the brain.A perusal of these signals have tobe made with reference to earlier

inputs stored as memory. Aftercomparing, contrasting andevaluating new sensations,decisions have to be made andintimated to the motor limb forappropriate reactions. The cortexof the cerebrum does all this veryelegantly. It has tiny units, theneurons, modified to performtheir specified bit in the networkthat runs the show. How exactly

THE GREY TERRAIN 31

The organisational head

32 MIND MASTER

The six layered cortex

# •••••

1 Tangentiallayer•..••• '.':<~"""'';''':''

these cellular master­

pieces do so is the elusivequestion asked over andover again. Over the cen­turies no technique hasbeen spared - all possible'stones turned' to get apeep into this 'greatrevealed knot' (as SirCharles Scott Sherringtoncalled it).

For biologists the seven­teenth century was aneventful epoch as the in­vention of the microscopehad extended the power ofvision substantially. Usingthe early crude instru­ment, in 1776, FranciscoGENN ARI - an Italian

scientist first reported thearchitecture of the cerebralcortex. A detailed struc­ture of a 'stria' of the occipital cortex, the one that still carrieshis name was painstakingly described. It took another 50years for better microscopes to be available to arrive at mean­ingful observations on the cortex. The 'Laminar pattern' ofthe cortex, suggesting a layered outlay of cells was describedin 1840 by Jules Gabriel Francois BAILLARGER (1809-1890)and a little later by Theodor Herman MEYNERT (1833-1892).In the last decade of the eighteenth century anotherbreakthrough gave an impetus to this research. Reliable tech­niques for specifically staining neurons were developed.Cytochemical work was stImulated by procedures perfectedby cytologists like Camillo Golgi in Italy, Santiago R.y.Cajalin Spain and Franz NISSL (1860-1919) and Karl WEIGERT

THE GREY TERRAIN 33

Pyramidal (left) and stellate (right) neuron

(1843-1904) in Germany. The hazy patterns uftder earlymicroscopes could now be seen with clarity and describedwith greater precision. The amplified 'laminar structure'could be discerned as stacks of specialised neurons. Variousregions of the cortex showed differences in the pattern of cellassemblies. All the same, a generalised pattern could be madeout. Based on staining techniques of Golgi, Nissl and Weigert,a six layered scheme was proposed by Korbinian BRODMAN(1868-1918).The cellular map of the cortex was seen as varia­tions on a cell organisation of six horizontal blocks. Thisscheme has found wide acceptance. The descriptive clas­sification of cells is so apt that the scheme has survived,though no clear functional correlates could be established.

The human cerebral cortex, spanning a surface of 2850 cm2

is compacted to occupy the volume ofa mere 300 cm3. Foldingon itself several times, to occupy the limited intra cranialspace available, the cortex is formed of closely packed cells.Densely populated, a cortical region of 1 mm2 and 2.5 mmdeep may contain as many as 60,000 neurons. However, the

34 MIND MASTER

density of cells is not uniform allover. Each of the neuronmakes multiple contacts to form an immense mesh of inter­connected units. These primary functional units are essential­ly of two types - the pyramidal neurons and the stellateneurons. Triangular in shape, with a long dendrite as theapex, and with sp:routs of basal dendrites, are all pYramidalneurons. Wi th spine like extensions allover, called dendrites,the pyramidal neurons make profuse contacts. Varying insize to suit the local requirements these neurons may span adifferent amount of cortical depth. Together with their inter­connections a layout of pyramidal cells forms a 'columnar'unit. The other type of neuron, smaller, star-like in shape andfound in abundance, is the stellate neuron. Forming an in­tegral part of the whole of the cortex, these neurons are seenpreferentially distributed in the second and fourth layers ofthe cortical laminar pattern. Extremely accommodating,these cells shape themselves for best contacts. A type ofstellate cell is the 'basket neuron' - the one that has axons

~~ Horizontal

Neurogliaform .•

Different types of neurons

THE GREY TERRAIN 35

forming horizontal liaisons across to other cortical columns.The 'fusiform' type send out two large dendritic arms inexactly opposite directions and terminate in a rich flourish ofbranches. Forming intense local contacts are the 'neurogliabranches stellate neurons'. In addition, neurons that help outin special areas are 'the horizontal neurons (of Cajal)' and'Martinotti's neurons'. Apart from these predominating celltypes, there are many more neurons that form indispensiblelinks in the endeavour for transmitting messages. Tracing outthe trail of pulse, as a thought flows through, has been a longpursuit of many.

In 1870, Gustave T. FRITSCH (1838-1927) and Julius E.HITZIG (1838-1907)from Germany did a series of innovativeexperiments on dogs. They applied weak electrical currentsto the frontal region of the cerebral cortex of the animal. Theresult was fascinating - the response was seen in the muscleof the right side of the animal. Scientists were excited, notonly because this was a direct experimental proof of whatthey had been guessing from clinical observations, but alsobecause the technique had opened new doors. Another mapof the cortex could now be made - a functional one this time.

It was later found, that the mapping could be done the otherway round too. A part of the body could be stimulated (saya finger could be touched) and the electrical pulses generatedin the specific cortical region could be picked up. This methodhas turned out to be extremely enlightening. Starting withrecognizing primary areas involved in receiving direct infor­mation (the sensory areas) and the ones responsible for send­ing out orders to the muscles (the motor areas), many terrainsof the cortex have been charted out.

Some pathways which bring information from the senseorgans to these cortical areas have also been established. Theinformation from the surroundings is received via fourmodalities - the photoreceptors in the eyes receive light; thechemoreceptors on the tongue and in the nose receivechemical stimuli; the mechanoreceptor perceive changes in

36 MIND MASTER

THE GREY TERRAIN 37

pressure in the inner ear, skin or in the blood vessels; and thethennoreceptors perceive temperature changes on the skinand in the brain. Each of these receptors responds essentiallyto a unique type of signal and conveys information to adistinct part of the cortex. The perception has more to do withthe location where the information is filed in the brain, thanthe type of stimulus that causes the activity of the sensoryreceptor. For example: if the eyeball is pressed rather hard,the photoreceptors do manage to respond to the pressure.However, preception is a visual one - a diffuse sort of visualsensation is felt. Essentially, all receptors transform thestimulation into an electrical activity. The receptors act astransducers converting every stimulus to a change in thepermeability of the membrane to calcium, sodium and potas­sium ions. A small potential difference thus builds up withevery stimulation of the receptor, all culminating in a largepotential difference across the membrane -large enough tofire the neuron and send the pulse through appropriatepathway to specific sensory region of the cortex.

Areas of the cerebral cortex that are neither totally sensorynor motor, but seem to be linked to the higher functionsassociated with primary perceptions have been recognized.These areas are the ones that get indirect inputs - eitherstraight from the primary areas or via the switchboard of thebrain - the thalamus. To date, it appears that the cortexcould be sub-divided into 50 to 100 functional areas. We

appear to have a point to point correspondence of our sensa­tion in the cortical map - only the contribution is not exactlyproportioned. The map is rather distorted one. Some percep­tions of high priority, like sensations that demand to beidentified with clarity and distinction, find large repre­sentation on the cortex. For example, perceptions of fingertips, which are endowed with high sensitivity to what theytouch are mapped in a far larger area of the cortex than theback which is relatively less discriminatory to tactilesensations. Likewise the regions of the retina - the screen in

38

(I' !

EfJ~

MIND MASTER

THE GREY TERRAIN 39

Interpreting a sensation is like puttingtogether a jigsaw puzzle

the eye on.which an image is formed - find uneven repre­sentation in the visual cortex; the light falling on centralregion of the retina stimulates 35 times more cortical areathan a similar stimulation of the peripheral retinal region.The elegant discretion used by the cortex in amplifying cer­tain sensory inputs has worked wonders!

When this functional chart of the cortex is superimposedon its cellular mosaic it tells us a little more about how it is

organised. A nerve fibre that brings in the initial information,right up to the primary region of the cortex, spreads it locallythrough a couple of synaptic connections. The pulse speedsup in the layers of the cortex, through the cortical neurons,resulting in a local vertical spread of the message. Thepyramidal neurons playa significant role in this propagation.As the information sinks in further, it is transmitted laterallyas well through the stellate neurons. A perception is probablytaken in bits and pieces, processed in the cortex incorresponding tiny units and reorganised to give an overall

40

understanding of thestimulus. Taking up infor­mation in discrete piecesprobably help integratingmore than one sensation

in the same region or inone in the close vicinity.As a signal is transferredfrom one cortical area toanother, it is modified andappears to be more dif-

MIND MASTER

A patient being injected with a radioactive analogue beforeundergoing a PET brain scan and result of a PET scan. A superimposed

graphic picture identifies sections of the brain

fused than when the input was, but is now in an abstractform. The mystery of the cortical processing deepens asmessages pass out of the primary cortical areas to thoseinvolved in 'higher processing'. That brings us to the frontierof cortical research! No clear answers are yet available.Probably a technical breakthrough would help!

THE GREY TERRAIN 41

Of all the technical liaisons, the one between the computersand medical sciences has been a very fruitful one. Indeed,with the development of various scanning techniques like theCAT (Computerized Axial Tomography)scan or the PET(Positron Emission Tomography)scan the result has beenvery dramatic. A visual integration of images of thin slices ofinternal organs by computer stimulation has permitted ob­servation of living tissues in their full functional integrity.This was something long awaited - not only by clinicians,but also by biologists involved in research. Innovations al­lowing sharper and meaningful imaging have developed ata rapid pace. A landmark in ingenious imaging is thedevelopment of a technique that traces information flow inthe brain of work. In 1977, the Journal of Neurochemistrycarried a paper on mathematical modelling and animalstudies, describing a method that has developed into thesophisticated technique of PET. Louis SOKOLOFFdemonstrated that the behaviour of glucose in the brain couldbe analyzed to a great extent, accurately by trailing a similarmolecule. The analogue, the one that chemically behavedalmost like glucose was tagged with a radioactive carbon.This radiolabelled analogue - 14C-deoxyglucose when in­jected in the animal travels across the brain exactly as glucosedoes. The precursor 14C-deoxyglucose, however, is utilizedby the brain cells at a rate which is a bit slower than that atwhich glucose is consumed. As a result, radioactivity buildsup in all metabolically active cells. Neurons at work at anygiven time, show a high rate of metabolism as compared tocells not involved and consequently accumulate more ofradioactivity within. The radioactiJJity can be picked up toreconstruct a metabolic map of the brain. It has not taken longto extend this technique to the human system - the analogueused was absolutely harmless 18F labelled 2-fluoro-2­deoxyglucose which emits positron. Busy neuronal as­semblies accumulate labelled 2-fluoro-2-deoxyglucose for ashort time, while the positrons emitted by the same help scanthe exact location of these cell assemblies. Totally non-

42 MIND MASTER

invasive, reading the cellular activity of a living brain, thistechnique has a lot to offer to clinicians and to those interestedin knowing where and how exactly signals flow when thebrain performs a particular function. Questions like whichcells are stimulated when we speak or read, which neuronsare active when we try to focus our attention or to memorize,have not found clear answers yet. However technique likePET would bring us closer to the answers. In fact, PET maybe the break-through that we require to know about corticalinformation processing.

LearningTimes

small girl of seven stoodexpectantly on the porch,awaiting her teacher's ar-

rival. As she described it in herlater years, her tormented mindfelt like a ship lost in fog­without a compass or a soundingline- unable to know how far theharbour lay. She was special inmany respects. Lost in her silentdarkness, she had an urge tolearn, grope out towards light andcommunicate. This urge turnedher life into a miracle. With ateacher, who kindled her spirit,time and again, as she struggledthrough most unusual ways oflearning, she became a legend.The young girl was Ms.HellenKeller and her teacher wasMs.Anne Sullivan. Together theyset an inspiring example to manya young learner who struggledagainst odds. Inspite of totalbreakdown of audiovisual sig­nals, the development, not only oflanguage and speech, but alsocommunication of abstract ideaswas a triumph both for the teacherand the taught.

Those who have consciouslyfollowed the learning pattern innormal children would definitelynotice the role played by visualsand words provided by theadults and would appreciate the

44 MIND MASTER

incredible achievements of

Ms.Keller. For the little 'copycats' learning is often nothing butfollowing and imitating theparents. These early signalsprovided by the parents'imprint' faithfully in the nervenets of the young developingbrain. Unlike most other higheranimals, the human race is en­dowed with a prolonged

Ms. Hellen Keller childhood. Weare also blessed

with an instinct of strong paren­tal contribution to our developing young ones. This extendedhelplessness of infancy together with a strong sense ofresponsibility towards our children makes us human, excel­lent learners and untiring teachers. This combination willcontinue to enrich our generations to come. Learning inhuman beings, however, does not end with the end ofchildhood. We are learners for a life time!

The legend of 'Mahabharata' tells of many stories thathover on the edge of scientific credibility. An interestingepisode is that of 'Abhimanyu' who is supposed to haveacquired special skills while in his mother's womb. Thoughone finds no direct explanation for this, it is now well knownthat neurons do form basic neuronal circuits in response tothe molecular environment provided to them duringembryonic development. The neuronal cells in the foetusdivide at a very high rate - averaging no less than 250,000per minute. This large number of cells generated in earlyfoetal life, starts moving towards its destinations within thedeveloping brain. Giving young cells a helping hand arestar-shaped cells 'astrocytes' that act as cellular scaffolds. Asthey approach their legitimate location, the cells overhaulthemselves biochemically and settle down as matureneurons. The membrane of the cells get ready to conduct the

LEARNING TIMES 45

signals - a tall demand has to be met - freshness of thefunctional ability acquired has to be sustained throughoutlife, with very limited repair. No more cells are added now- on the other hand those which do not contribute to any ofthe brain function are lost perhaps forever. And during allthis hectic activity of settling down a social awareness amongcells also develop. Firm relationships are established withsome neighbours, while preliminary dialogue is initiatedwith others. Topographic positions with respect to eachother are identified. As the cells become more and more

specialized, acquire characteristic shape and functionalability, they become a confirmed part of a nerve net. Thecerebral hemispheres which lodge the nerves' nets for the

46 MIND MASTER

11m

"Finn relationships are established with some neighbours, whilepreliminary dialogue is initiated with others"

LEARNING TIMES 47

important function of the brain, acquire characteristic con­volutions fairly late during development.

At birth, a complete, preliminary complement of neuronalnetwork is already acquired. The raw material is ready,fundamentally the same in most of us, except for little naturalvariations. What is now left is moulding - experiences thatwill give us our individual qualities and capabilities. At thisstage, the brain is very labile. Though not many new addi­tions can be made in the cellular components, the quality ofjunctions among neurons, the synaptic connections can becontinuously remoulded. Retention of this brain plasticitytogether with enrichment of early neuronal network lay afoundation for learning ability. The natural potential is un­limited, now it is for the environment to strengthen certainneuronal circuits and dissociate others. An adequate nurtureof the flourishing nerve nets often overcomes the constraintsof genes within. So much for providing equal opportunitiesfor learning to each one of us!

In the early sixties David H. Hubel and Torsten N. WIESEL(1924-)both then at Harvard Medical School, performed a setof elegant experiments that would fetch them the Nobel Prizein the years to come. Using the visual system of cat as anexperimental model, they demonstrated, electrophysiologi­cally, the role played by environmental factors duringdevelopment of neurons. They identified neurons in thevisual cortex - the area in the brain where visual information

is processed and that develops only in response to stimula­tion of eyes by light. When vision in one eye was artificiallyblocked, the number of neurons in the visual cortex thatresponded to stimulation of that particular eye alone,declined in number. As a result the binocular vision was lost.

This failure was found to be persistent. When the artificialblock was removed and the eye was allowed to see, itremained 'blinded'. Neurons of both the eyes were able tosend in the signals yet the brain could not process those fromthe deprived eye. Though the cat had both the eyes function-

48 MIND MASTER

David H Hubel (left) and Torsten N Wiesel (right) demonstrated therole played by external stimulus like light

aI, only one eye could see! The genetic potential that was­could never be realized - it was lost, once for all.

Carl R. OLSON and Ralph D. FREEMAN of the Universityof California, Berkeley, added a new dimension of time to thisstudy. Based on electrophysiological experiments it was pos­sible to demonstrate that stimulation of eye by light was verycrucial at a particular stage in development of the visualcortex. If signals don't arrive on time - the bus is missedforever. Anatomical and electrical links between neurons that

carry information from retina to the visual cortex fail to

LEARNING TIMES 49

develop. If appropriate connections are not made in thecritical period - none develop. This failure persists evenafter the deprivation is overcome at a later stage. Theneuronal outlay in the 'critical period' is open to sensoryinputs. If no inputs are available, not many synaptic connec­tions are made. On the other hand, if information is allowedto permeate, the anatomical modulations can develop toassimilate it - making neurons further receptive to newerconnections. A good analogy for how neuronal plasticityoperates is that of rain water flowing down a wet terrain.Small multiple rivulets originate, to begin with, in largenumbers. If water continues to flow through these, deeperfurrows appear and a bubbling stream is formed - now ableto allow the flow of more and more water. If water flows as

a trickle through these rivulets only a feeble water way ismade; sensory inputs at specific moments help, like the flow­ing water, to establish good synaptic connections - the deepfurrows for ample water to flow through.

The most important unit of brain plasticity, the synapse,has been a focus for molecular analysis. As a new pathwayfor information flow is laid out, the liaison between twoneurons has to be initiated. Each neuron begins with sendingout numerous microscopic branches - some that are able tofacilitate a contact while others reach out in vain. Outgrowthsof neurons that are unable to establish a definite dialoguewith other neurons are often retracted. The branches that

firmly initiate communication are strengthened at the cel­lular level. Learning involves laying out and enforcing ofcellular contacts to form appropriate neuronal tracts. It is aquestion of establishing a right connection. How many pos­sible arborisations of the cell can appear in the first place iswhat determines how receptive is the brain to learning. Morethe cellular spikes available for putative neuronal pathway,better is a chance of a fruitful contact which would allow flow

of signals. A receptive brain is probably the one with largenumber of neurons ready to change their shape and size to

50 MIND MASTER

Neuronal plasticity can be compared with rain water flowingdown a wet terrain

LEARNING TIMES 51

reach out as much as possible. Recentl y, Chi ya AOKI (CornellUniversity) and Philip SIETEVITZ (Rockefeller University)looked for molecules involved in the change in shape of theneurons - the molecules that would contribute to fine

wiring of the brain during learning. They extended the workinitiated by Hubel and Wiesel on the cat visual system. Thesebiochemical studies have helped identify a neuron-specificprotein molecule which seems to participate in the microevents leading to the change in the shape of cells. This proteinnamed as MAP-2 is closely associated with the organelles thatmaintain the spatial integrity of the cell - the cytoskeletalelements. It appears to be the biochemical modification ofMAP-2 protein that helps the neurons to send out links toother cells. The MAP-2 proteins are the first of the molecularclues to what gives us our life-long learning ability. This isthe beginning of our attempt to understand how our sur­roundings, the ways of our lives, and the people we meet aremirrored in our brain - sometimes irreversibly.

Interestingly, one of the first lessons we learn, fairly earlyin infancy, is to ignore. That helps us to be habituated to oursurroundings. Stimuli that are integral part of our environ­ment, the ones which present themselves time and again,evoke little response. Learning to accept these stimuli astrivial, however, does not seem to involve a major restructur­ing of the synaptic connectivity. Instead, a subtle change inmolecular sensitivity suffices. V. CASTELLUCCI, M. KLEINand E. KANDEL from Columbia University have pinned thischange in responsiveness to simple calcium ions and theirregulation. A stimulated neuron communicates with anotherby releasing the chemical messengers, the neurotransmitters.For bags of neurotransmitters to burst out into the cleft of thesynapse, a flux of calcium ions into the cell is obligatory. Withevery signal, the neuronal membrane exhibits an alteredpermeability to calcium at the synaptic end. The calcium ionsrush into the cell and help the tiny vesicles filled withneurotransmitters to fuse with the cell membrane and put out

52

ATI-JELETE

TRAINING CENTRE

MIND MASTER

their content. Repeated stimulation of a similar naturedepresses the influx of calcium ions by closing the cellulargates to its entry. This in turn adversely affects the release oftransmitter substances that carry forth the signals. Learningto ignore stimuli that have little consequences involve suchsimple short term modulations, with few gross changes. Asimilar modulation seems to take place when we learn torespond to obviously unpleasant stimuli. Once exposed to anobnoxious experience, we learn to be more alert. Sensitisationto strong, effectively dangerous signals has been seen toresult in calcium ion modulation that increases transmitter

release and a corresponding behavioural alteration. Learningsimple tricks for survival, along with more complex ones thecellular elements of our sensorium builds up a store of

LEARNING TIMES 53

A good diet helps child to learn early

information. Our learning banks heavily on this stored inputof the adaptive changes in our behaviour resulting from ourexperience, to be recalled at an opportune time; the data thatare stored as memory form an integral part of our learningprocess.

A receptive learner - with a brain alive with agile cells- and a patient teacher is, no doubt the combination thatstrikes best. However, the environment that brings out thebest in us is more difficult to define. The best studied pre­requisite for a healthy growth of the brain is nutrition. Adeveloping foetal brain is known to be sensitive to maternaldiet. The 15th to 20th week after conception is the periodwhen the foetal neurons are being formed. For a healthyfoetal brain to be formed the maternal diet in this sensitive

period should be of high nutritive value - rich in protein.

54 MIND MASTER

Deprivation at this stage can leave scars on the mentalcapabilities of the child forever. Malnutrition during first 18months of the baby causes permanent damages - the loss ofneurons - which cannot be replaced. At a later stage, anempty stomach makes a child a poor performer; a good dietcan immediately improve the situation substantially. Apartfrom a good protein rich meal, the freedom to explore, inventand express is probably what is most needed for the develop­ment of a brain most receptive to learning. Unburdening thechildren of continuous bookish inputs and stimulating themto ask questions will, most likely, make them the bestlearners!

•

"

. -- --.---.------ ...- ----

Breakingthe

Silence

OME days dawn with ageneral feeling of well-beingmaking spirits soar for no

specific reason. So much so thateven travel in an overcrowded

public transport does not seem abad proposition. In fact, it turnsout to be an enriching experience!The sheer variety of people, onecomes across, is rich material forobservation and contemplationfor the next twenty minutes of jos­tling. And if one chances to beplaced near a pair of chatterboxes,the journey is an absolute success!An unusual chance is being seatednear I silent' chatterboxes, - thosewho use their fingers and palmsto gesture out to each other.Laughing to themselves, they area world apart, as the rest watch onin awe and bafflement. Trying todecipher the rapid movements oftheir digits turns out to be quitefrustrating for the uninitiated.However, their efficient com­munication skills fail them sud­

denly when somebody with aspecial faculty approaches. Theirbliss is broken by the spokenword.

Speech, the mode of com­munication, used so freely, oftenwith little reverence to what its

effect may be, is not for some. Andthese few we meet sometimes,

56 MIND MASTER

The 'silent' chatterboxes, are a world apart

struggling to reach out, sharply focus the importance of thefaculty of speech in our social existence. These few who bravethe din of the world in silence are also the ones who have

helped us most in our quest to find out more about the specialcapacity of ours to form words and sentences. Simultaneous­ly, breaking their unfortunate silence is a major challenge tothe world of science.

Sound that conveys quickly, what is perceived by one toanother, is an innate requirement of interdependent in­dividuals. Calls varying in pitches, loudness and durationare used by a large number in the animal world - for alertingeach other against danger, for aggression or for wooing apartner. The use of sound acquires an exclusive quality inhumanbeings. The need to understand each other seems to

BREAKING THE SILENCE 57

be far more pressing. For an early evolving man, strugglingagainst the harsh realities, finding and capturing foodneeded to be strategically planned. Small hunting groups,with individuals playing specified roles were probablyformed. Effective communication within these groups was aprerequisite of a successful hunt and ultimate survival. Anarticulate sequence of sounds was definitely the best modeof expression, while hearing was an ideal way of receivingsignals, as communication could be established even in thedark. Foundation of the faculty that developed into fullyarticulate speech was probably laid in those hazy, difficultdays. Evidence collected from bony fossils of early hominidskulls suggest that our ancestors had started speaking about1.5 million years ago. The brain of our ancient cousin Homoerectus, probably, did have a centre for speech. These centresof our brain have given us an edge over other primates. Theskill of speech has bloomed with our species so much so thatat times itneeds to be given a novel name-'noise pollution'!

The verbal flow that runs so easily involves complicatedneuronal functions. Thoughts or ideas that are to be con­veyed, written words that are to be read out, or a heard wordthat is to be repeated, all need to be transcribed into soundwaves. These sound waves should be such that they enablethe listener not only to recapture the meaning but also toperceive the emotions behind the spoken words. A transferof perceptions from one person's brain to that of others isexpected to take place via this acoustic exercise. Waves ofsound of a definite quality can be generated by each of uswith the help of our 'sound box' or larynx.

Made up of a combination of nine cartilages that are heldtogether by flexible muscles and ligaments, the larynx canassume various types of configurations during speech. Theactual wave of audible sound is produced when the airpassing out of our lungs is blocked and released successivelyby a pair of voice producing organs - 'vocal cords'. Depend­ing on the characteristics of the larynx and the vocal cords

58 MIND MASTER

The larynx

each one of us can

produce a wave ofsound of certain fun­

__ Hyoid bone I damentalfrequency­this determine" the

Throid cartilage I basic quality of our(Adam's apple) voice. Further mani­pulations of laryngealmuscles provide ups

Thyroidgland I and downs in our

tones - expressingour emotions. As the

waves of sound passout through the vocaltract the various partsof the mouth help ar-ticulate it into words

with right intonations.Generation of words

with correct meaning,right diction and desired overtones requires that all themuscles and ligaments of the vocal apparatus receive preciseinstructions, well under the control of the speaker.

Involved in one or the other aspect of the speech produc­tion are a little more than forty different muscles of the vocaltract - all supplied by millions of nerve fibres running downfrom the brain. Forming the nerves that bring in the messagesare the motor neurons - in turn receiving pulses of informa­tion from the cerebral cortex. Extending across in an arc likefashion, between the two ears, is a special part of the cerebralcortex - the motor part. This area governs, in general, themovements of the muscles in our body. On either side of thebrain, there is part of the motor cortex, where impulses thatare sent to the speech muscles are evoked. A damage to thislocation in the brain causes disorders of speech or 'aphasia'- as no signals can be transmitted to the vocal tract muscles.

BREAKING THE SILENCE 59

Area for speech

The person with adamage to this part ofthe motor cortex can

comprehend written orspoken words but isunable to form words

in response. Aphasiacan be due to even

more serious yet subtlereasons. Damage tosome other regions ofthe cerebral cortexcould affect com­

prehensive and articu­late speech. A painfullylaborious study of the

brain anatomy of normal and aphasic individuals has, in fact,helped map the other important centres in the brain helpingin our verbal outflow!

The middle of the nineteenth century witnessed severaloriginal scientists paving the path for cond usive discoveries.The early ideas, about the location of lorgan of speech' wereput forward by the phrenologist F.J.GALL(1758-1828). Hesuggested the frontal lobe of the cerebral cortex as the site.Marc D AX,a general practitioner in France went a step aheadand proposed that the frontal lobe of the left hemisphere ofthe cortex was alone involved. These observations passedun-noticed till Paul BROCA (1824-1880)brought them up byhis study. Well known for his progressive scientific ideas, aneurosurgeon by profession, Paul Broca had a keen interestin anthropology. In a discouraging environment he laid thefoundation for research in anthropology in France. In hislifetime he made a fine collection and a biometric study ofnumerous brain specimens. Brains of all sorts and sizes, ofapes and men, of old and young, of normal and abnormalindividuals comprised his remarkable collection. Scrutinis-

60 MIND MASTER

'Broca's Area'

ing and measuringmeticulously, Brocarecorded several interest­

ing observations - someso important that theylinked his name to a part ofour brain forever. He iden­tified a well defined areain the frontal lobe of the

cortex that was invariablydamaged in aphasic in­dividuals, but was intactin normal ones. Further, asimilar damage on theright side did not cause.any speech defect. The twohemispheres, though ap­parentI y forming identical halves of the brain, seem to havefunctional preferences. The speech center, identified con­clusively by Broca, is little anterior to the motor centersresponsible for movement of muscles for speech and isknown after its discoverer as 'Broca's area'. Indispensable fornormal speech, the Broca's area, is the center that co-or­dinates facial muscle movements and the perceptions of thebrain to form strings of words.

The close proximity of Broca's area and the motor centerfor speech suggests a very close link between the two. Sointimate is their relationship that often a damage caused tothe Broca's area leaves the adjacent motor area also impaired.The result is facial paralysis with loss in speech. On the otherhand, there are situations where a lesion is restricted toBroca's area alone. The speech disorder that arises, known as'Broca's aphasia', enables the individuals to use the facialmuscles very efficiently for vocal functions other than artiru­late speech. Singing without a hitch is possible for them, butwords can be pronounced slowly and with utmost difficulty.

BREAKING THE SILENCE 61

Manifestation of Broca's aphasia

The speaker can convey the meaning by forming telegraphicsentences - with some words missing. Delinked words andgrammatically incorrect sentences are marked features ofBroca's aphasia. Such failure persists even when it comesdown to putting words on paper. Surprisingly, however, thecomprehension of language is not much affected. Apparent­ly, understanding the language is not really a function of theBroca's area - yet it is the link between what is com­prehended and what, in turn, is actually said. The centerwhere all aspects of language are taken care of is a distinctone - though well connected to the Broca's area.

In man, the faculty of speech has evolved to almost theultimate. Words often convey more than what they actuallymean. The use of phrases and idioms add beauty as well assymbolism to speech. The phrases used are relevant if under­stood; if not, they mean something totally out of context! Theappreciation of subtle analogies that we use in our languagerequire a higher neuronal function. Use of some words thatcan have far more perceptual implication than what they

62 MIND MASTER

'Wernicke's Area'

literally mean requires a dif­ferent level of cerebral in­

tegration. The locus that isinvolved in adding thisflourish of language to ourspeech is a distinct one. Thiscenter, where our knowledgeof language and sensory as­sociation with words is in­

tegrated, was identified by ayoung German scientist CarlWERNICKE (1848-1905). Atthe age of twentyfour, he pub­lished his conclusions based

on the study of aphasic in­dividuals of a special type.The individuals, the ones with 'Wernicke's aphasia', couldspeak with a good flow of words but with inappropriateexpressions. Meaning conveyed is not exact, words used arecorrect but irrelevant. In such individuals the area respon­sible for the language used is damaged. Wernicke identifiedthis locale in the temporal lobe of the cerebral cortex, on theleft side of the brain. It is called Wernicke's area ever since.

As expected, nerve bundles connect this area to Broca's area- the anatomical bridge that is formed comprises the' ar­cuate fasciculus'. Wernicke's area is also where visual and

auditory information are pooled in - the most obligatoryinput when it comes to reading and writing!

In 1989 the new edition of the Oxford English Dictionarywas prepared by J.A.5IMPSON and E.5.C. WEINER. Listingabout 2.4 million words, spanning 21,728 pages, its twentyvolumes have all that goes in to make the English language.Each word listed has a meaning in itself and when jumbledwith few other it often conveys more. However, the word mixhas to follow a certain linguistic conventions, which are, infact universal and form the basis for languages used the

BREAKING THE SILENCE 63

world over. These fundamentals that have evolved over the

ages, need to be appreciated by all who use the language! Theuttered words, when knit in the invariant yarn of grammar,convert the mere sound waves produced by our vocal cordsinto a flowing language. In the first place the vocal apparatusneeds to be trained in phonetics - each word prod uced musthave a correct sound. The sequencing of words must followthe rules of syntax so that sentences are correctly formed. Onthe other hand the listener should have a prior knowledge ofsemantics - so that no misinterpretation of sentences takesplace. And the two in conversation should be pragmatic ­sequencing their sentences by anticipating the informationneeded to be supplied for effective communication. Thisframework of grammar that is the backbone of our com­munication skills, needs to be laid in the form of the neuronalnetwork of our brain - as circuits that send signals to thevocal apparatus. In addition, information specific to the lan­guage learned must be incorporated in this scheme. Acquisi­tion of a language is no simple task! An intense effort needsto be made for it - all human infants do make it! Tracing thedevelopment of language in children provides some insightinto this higher function of our brain.

A toddler of two is a bundle of pleasure, especially as hisverbal skills seem to be breaking through. NQrmal childrenby two years have a vocabulary of about 300 words. By thetime they are five they would have picked up no less than2500 words. The rapidity with which the linguistic capacityblooms, makes one suspect an instinctive basis for it. Anexponent of this point of view is Noam CHOMSKY, a notedlinguist from the Massachusetts Institute of Technology.Chomsky proposes that man has a unique competence tolearn a language - a gift no other animal is blessed with. Thefundamental grammar which is a universal scaffolding for allthe languages, is there within us, right from birth. Closelyfollowing is the proposition that these linguistic principlesare ingrained in our genes - the master molecules carry the

64 MIND MASTER

A child learns to speak by hearing and mimicking

ultimate blue-prints of our verbal capabilities. The issue,however, is not free from controversy, as there is an alterna­tive school of thought. Several psychologists, including B.F.SKINNER from Harvard, believe, that like so many otherfaculties we acquire, language too is learned by trial anderror. Human infants are not endowed with exclusive

powers, but only general mental faculties, and the grammaris engraved as a result of an exposure to specific linguisticexperiences. The words an infant hears and its own efforts toinculcate them forms his vocabulary. A 'reward' offered bythe teachers of language around them encou rages them to usecertain sounds while a negative response discourages use ofothers. It is a fairly difficult controversy to resolve. Experi­ments are hard to formulate and the results obtained are

equally difficult to interpret.

BREAKING THE SILENCE 65

The early 1970s witnessed initiation of research on infantspeech perception. This task of tracing the development oflinguistic competence of young ones was a complicated one.To begin with, speech signal itself is complex, each formingan acoustic unit. The energy stored in each of these acousticunits can be recorded as a 'spectrogram' - in terms offrequen­cy of the sound waves produced. Variations in this acoustic'signature', the spectrogram, is what gives rise to small recog­nisable phonetic differences. The two words 'pin' and 'bin'differ in a single 'phoneme'. For perception of such small'phonemic' differences the speaker must provide distinct andprecise acoustic information. One acoustic clue that helpsperception is the 'voice onset time' - the time interval be­tween the release of the air and the onset of vocal cordvibrations - a voiceless information that tells the listener a

lot. P.o. EIMAS and co-workers from Brown University havedemonstrated that infants can indeed perceive this importantinformation held by the' voice onset time'. In addi tion, speechsounds can be perceived as different, distinct categories. Asound 'BAH' said with a minor variation in 'voice onset time'

is still recognized as 'BAH'. It can be distinguished decisivelyfrom the sound 'P AH', which has a different voice onset time.Based on these findings linguists have proposed an'Innate­ness Hypothesis' which suggests that, very like an adult, theinfants can discriminate specific speech sounds. This abilityhas little to do with their auditory sensitivity but is becauseof the inbuilt linguistic disposition. Infants all over the world,whatever their native language, have these initial dis­criminatory powers. However, there are several speechsounds that babies fail to recognize as distinct.

Working their way up, on the little they start with, theyoung learners catch up soon with the adults. For this it isobligatory that a helping hand is available all throughout­an on-going verbal rapport is maintained. Knowingly orunknowingly, adults simplify their language while address­ing the children - words used are phonetically simple,

66 MIND MASTER

sweetlike

I eateat Ram

Ram likesI like sweet mango

I mango

sweet mango

sentences are short and are mostly in form of questions,pitches are higher and often intonations are exaggerated.This restructured' care taker' speech form red uces the strainon the young learners. Their non-coherent babbling is soonreplaced by a single word sentence. The next is a phase oftwo-word sentences. Following soon is a stage of telegraphicspeech and in no time the verbal flow is at its best. At eachstage, probably, word forms are ingrained in the micro­architecture of the brain. All throughout, the little learnersearnestly participate in conversations, practice jumbling ofwords when left to themselves and experiment with them atopportune moments. The response of adults to all this is mostimportant - harsh corrections delay the development, anencouraging linguistic environment alone lets the youngbloom. This environment modulates the early broadcapacities into more specific ones.

The perceptual abilities of the infants narrow down aschildren are continuously exposed to their mother tongue. Astime passes, acoustic discrimination abilities not required for

BREAKING THE SILENCE 67

speech in native language are erased. However, this loss isnot permanent. The vocal cords also gear up to form phoneticsounds characteristic to the native language. A child growingwith one language sometimes has the vocal tract so attunedto certain types of phonetic sounds, that a language learnedlater carries a reflection of this early training - the laterlearned language is spoken with a strong native accent. Abilingual child, on the other hand, is able to retain a certainflexibility of muscles of the vocal apparatus that can be easilymoulded into the accent of a foreign language. The adultlinguistic flourish is a result of what was acquired in the daysgone by and the on-going process of enriching through per­sonal inputs. The acoustic information that a word providesis relayed via the ear to the brain, right to the area thatperceives it. This area is a special part of the cerebral cortex- the primary auditory area. Links of this area stretch out tothe Wernicke's area. Bundles of nerve fibres, the 'arcuatefasciculus', convey the perceptions from Wernicke's area toBroca's area - the region in charge of forming phoneticallycorrect, articulate words. It does so by sending signals via themotor region of the cortex to the vocal apparatus. With everyrepetition of a new word such a pathway strengthens brainmicro-architecture, involving also the memory circuit, andultimately the word becomes a part of the vocabulary store.

Reading too contributes to linguistic ability of the adult.Neuroscientists have worked out the basics of neural path­way that integrates this input. Visually imprinted throughthe eyes, signals of a read word are initially sensed by thebrain at the primary visual cortex. In close vicinity is animportant convolution of the cerebral cortex - the angulargyrus - the part that aids in information integration. At theangular gyrus the visual perception of the word is matchedwith the auditory form of word in the Wernicke's area.Impulses then traverse the circuit involving Broca's speechstation and motor cortex, relaying commands to the vocalapparatus to read out the words. Words that need not be

68 MIND MASTER

repeated or spoken aloud may be simply perceived, referredto the Wernicke's area and stored in memory - to be recalledwhen necessary. This criss-crossing of neuronal circuits con­necting several functional foci of the brain all intimatelylinked with the language centre make a language much morethan uttering just grammatically correct sounds! Tracingprecisely these complicated circuits is a challenge to modernneurobiology.

One access to the maze of the mind is an electrical one. The

year 1857 brought brain research to a new threshold whenthe English physician Richard CATON discovered existenceof rhythmic electrical currents in the brain. The realbreakthrough, however, was when Hans BERGER (1873­1941) in 1920, obtained a tracing of them - a wave in thebrain could be recorded as an electroencephalogram (EEG).This electr~al recording tells of all possible neuronal events

BREAKING THE SILENCE

relaxed'

;r\"'w,rl"....,w~\'IIrlrVlf(lry~\W,\·lmr1\~~Isleep

coma

69

EEG of a person being recorded (left), and typical wavepatterns representing relaxed, sleep and coma states (right)

going on in the brain - that makes its interpretation ratherdifficult! The electrode that is placed on a particular regionof the scalp not only records with clarity the activity ofneurons in its vicinity but also a lot of 'noise'. Computeriza­tion of the system has helped averaging out the 'noise' andmeaningful recordings of a single mental operation can nowbe obtained as 'event related brain potentials' or ERP's. In1984, M.KUTAS and S.A.HILLYARD reported an interestingobservation - a very specific large negative ERP could berecorded whenever wrong words were presented to the sub­jects. The ERP was recorded with presentation of each word.Towards the end of the sentence a word that made the

sentence a nonsensical one was presented. This elici ted anelectrical pulse that had a negative potential and a peak at400 micro volt. Anomalies of grammar could elicit this 'N400wave' - a single word is capable to alter electrical activity ofthe neuron! The 'N400 wave' offer a new tool to unravel the

neuronal activity that helps us comprehend the meanings ofthe words. Such an approach would surely bring us closer tounderstanding our linguistic competence!

l~

Memory•

Muslngs

S the American cos­

mologist Carl SAGAN(1934- ), puts it, /I intel-

ligence is not information alone,but also judgement, the manner inwhich information is coordinatedand used. Still, the amount of in­formation to which we have ac­cess is one index of our

intelligence". This capacity tostore information, accessible in­stantly on demand has anotherpopular name, 'memory'.Memory, no doubt, has been oneof the major, though not the only,index of measuring intelligence.Regrettably, more often than not,knowingly or unknowingly, thisindex dominates our criticalevaluation of individual com­

petence in school and college ex­aminations. This property of ourbrain, which plays such an impor­tant role in our social and per­sonal existence, has been verydifficult to study and it is onlyrecently that more definite infor­mation has become available.

A set of early experiments onmemory in this century was car­ried out by the well knownpsychologist Karl LASHLEY. Hiswork culminated in an essay en­titled 'In search of engram'. How­ever, the essay did little toencourage further studies on

MEMORY MUSINGS 71

Persistent sensory information helps developnetNorkconnections

memory, as it suggested that 'engram' the 'memory traces'did not exist. Memory appeared to be hazily spread-thediffused property of the brain - inaccessible to any concreteexperimental approach thus bringing the scientists to a deadend. It was the work of two other psychologists, Donald O.HEBB of Montreal and Jerzy KONaRSKI of Poland, thatrevived specific interest in 'memory cells'. Their suggestion,that a group of cells made very definite contacts to form'memory circuits', opened new aveneues of research. Soonreports poured in to substantiate the idea that the brain hadvibrant cell assemblies, making connections of permanentnature in response to persistent sensory information drilledin. On the other hand, few and inconsistent sensory inputsdo little to keep a neuronal connection intact for a significant

72 MIND MASTER

time. That is to say, in simple terms; if one doesn't read one'slesson frequently enough - memory fails!. The visuals wesee, the music we hear, the aroma we inhale all pass throughneuronal pathways distributed allover the cerebral cortexthat transforms these experiences into things to be remem­bered. However, decisions as to which perception is worthremembering is made in the structures situated d~eper in thebrain.

Classified as a part of the 'limbic system', sitting deepinside, snugly against the almond shaped 'amygdala' is the'hippocampus'. As the name suggests it looks like a tiny' seahorse'. Each one of these structure is lodged on either side ofthe basal region of the brain. Very close by is the edge of thetemporal lobe-as it folds inwards and upwards on thelateral sides of the brain. It is to the hippocampus that impor­tant sensory pathways from the cerebral cortex report theirpen;:eptions. If the perception is strong enough to stimulatethe hippocampus, a fairly strong neuronal connection is es­tablished in the cortical region that can be replayed. Thereplay could bring back more than one sensory information- as circuits are often interconnected. An advertisement seen

several times over, makes a strong impression of both, thevisual and the jingle. Hippocampus helps store these impres­sions. A similar tune heard later brings back in a flash the

Thalamus

Hypothalamus

. Amygdala ~ OlfaCtory bulbHIppocampus Pituitary gland

The limbic system

MEMORY MUSINGS 73

visual too - as memory is not stored in isolated sets ofneurons but as superbly mixed, interlinked pathways ­criss-crossing and stimulating each other. These are the targetpathways of a product campaign - aiming at making theadvertisement an experience to be remembered - though thevisuals and the tune may have little to do with the productpropagated!

Hippocampus is not the only organ so intricately control­ling our ability to store inputs. Another very important sta­tion involved is the thalamus located in the centre of the

brain. Thalamus along with another partner, hypothalamusforms the connecting part of the brain - the diencephelon or'between brain'. It links the middle part of the brain (mesen­cephelon) with its front part - the forebrain. The thalamusis the station that responds to a signal demanding recall ofthe stored cortical treasure! Well ramified connections from

the thalamus touch almost all the sensory pathwaysengraved as memories. It is the thalamus that passes on theinformation to the cortex as to which' action replay' shouldbe switched on. An appropriate neuronal circuit touchedupon makes us rush back through time, to recapture anexperience of the days gone by!

Remembrances of things past bring back associated emo­tions too. Emotionally touching encounters are better remem­bered. In fact, impressions made when lit with emotions likerage or fear are often out of proportion. This intermixing ofemotions and sensory information is a complex interaction- a difficult proposition for investigation. However, experi­ments on other primates offer some information. A studyconducted by H. KHIVER and P.c. BUey on monkeys sug­gest that' amygdala' is important for development of associa­tion between memories and emotions. With its anatomical

partner 'hippocampus', the amygdala forms the structurethat surrounds the hypothalamus. The hypothalamus rulesour emotion totally and is in league with the amygdala.Together they form the complex that gives an emotional tone

74 MIND MASTER

Emotions like fear are usually remembered for a long time

---. -.-. - -- - -- - ..- .- -- - --- -- ..--. -- --- .-

MEMORY MUSINGS 75

Amygdala selects experiences for long or shortterm rememberance

to the experiences that are remembered. c.B. PERT, andcolleagues have molecular evidences to support this roleplayed by amygdala. They further proposed that amygdala,being an anatomical link between parts of the brain whichperceive and those which govern emotions, may playa roleof a 'selector'. Anything emotionally important receives'selective attention' and is perceived better. A sensitive per­ception helps remembering an experience better. This deli­cate role of amygdala makes it an important locale in thescheme of registering and retaining worthwhile information.

Reducing an experience to the level of molecular interaC­tions, and an individualised attribute like memory to a merenetwork of neurons makes one a trifle uncomfortable. This

'reductionist' way of analysis has its own drawbacks. Yet, asthe well known Canadian psychologist Donald O. Hebb put

76 MIND MASTER

it - "this is not degrading mind to matter. Instead it isupgrading the properties of matter to account for the mind".Explanations for storing memories are, therefore, sought inthe circuits of the neurons, their synaptic termini and in themolecules participating at these connection.

There is a lot of information we hold for transient moments

- not for long duration. Such inputs seem to be held for ashort time by reverberating circuits in our brain. As tim ulatedneuron starts off a train of pulses that in turn stimulates ittime and again. As the impulse vibrates through repeatedly,the information is held on for a few seconds or a few minutes.

The sensation persists sometimes for a slightly longer dura­tion too. At times as the pulses die down no permanent tracesare left, while in some cases a consolidation follows - put­ting information into the form that persists as long termmemory. Neurophysiologists expect the synaptic connec­tions to playa role in this input, the one that we rememberfor a longer time.

The synaptic junctions in the hippocampus have been atarget of investigations for memory molecules. In the earlyseventies Timothy V. BLISS and Terje LOMO from London,reported some interesting features of synaptic communica­tions in the hippocampus in response to strong stimulation.Transmissions in these stimulated neurons were more effec­

tive and lasted longer. A scientific phrase 'long term poten­tiation (LTP)' was coined to express this unusual mode ofkeeping signals alive for a longer time.

As in the other regions of the brain, the message runningthrough the neurons of the hippocampus is in the form of anelectrical code, travelling down the length of the long arm ofneuron - the axon. The neuron that receives these molecular

messengers - the post synaptic neuron - is in turn fired tocarry the message further down. In most other parts of thebrain the neurotransmitters, after delivering the messagefade out - either broken down enzymatically or reabsorbedby cells. In the hippocampus region, however, these neuroac-

MEMORY MUSINGS 77

Signals receiv;d at hippocampus are kept alivefor a longer duration

tive substances are released at the synapse in larger quantities- they insist on reading out the messages for a longer periodof time. The post synaptic neuron, the one receiving themessages, responds by showing far more sustained excita­tion. In turn, it also helps maintain the active state of neuronsending out the messenger molecules. This establisheddialogue holds the information being transmitted for a long

78 MIND MASTER

Neurotransmitters bind to receptors at synaptic cleft

MEMORY MUSINGS 79

electrophysiological change in the neuronal membrane. Thenet result of all this rigmarole is 'long term potentiation' ­the electrophysiological change in the neuronal membranethat is crucial for memory recall. The tip of the iceberg is insight! Rest of the molecular mechanism awaits further inves­tigations.

The insights of the eminent physiologist, Donand O. Hebbseems to carry more credibility now - with these recentfindings at the very molecular level. As early as in 1945, Prof.Hebb postulated that when cell A repeatedly and persistentlytakes part in firing cell B, some growth process or metabolicchanges take place either in one or in both the cells in such away that A's efficiency, to fire cell B, is increased.

Reports on synaptic memory molecules are the result ofresearches based on this hypothesis. Metabolic changes in­volving protein synthesis during learning have been con­clusively proven by elegant experiments of BernardAGRANOFF of University of Michigan. Allan JACOBSONand his colleagues reported the possibility of memory trans­fer from 'learned' hamsters to untrained ones by transferringthe ribonucleic acids. Other neurobiologists alsodemonstrated newly synthesisedribonucleic acids in braintissue of animals showing sustained learning activity.Ribonucleic acid formed by the brain was in definite amountsand of special type also. This special synthesis was furtherreflected in the appearance of a new type of protein, the newribonucleic acid being probably the one that carried the codefor the freshly synthesised protein. Scientists from Sweden,Holger HYDEN and P. LANGE performed delicate experi­ments to identify new proteins synthesised during learning.Details of exact involvement of fresh RN A and protein syn­thesised in memory are awaited ever since. Identification ofnew synaptic memory molecules may provide crucial piecesof the molecular jigsaw!

to,.' .. ----"-

The

BrightnessMarked

OME of us seem to be bornwith a little more than ourshare of good luck. We have

an extra blessing of meeting theright teacher at the right time. Anenvironment with ever guidingfather figures in the background,who have managed to strike acritical balance between givingfreedom and maintaining dis­cipline, is not what everybody isensured of. It is a bit of a goodfortune that does not have a

monetary substitute. Blessed withsuch a gift the human intellect canreach great heights. It is well ac­knowledged that the relationshipbetween mental ability and socio­economic success is a complexone. All the same, the humanmind relentlessly seeks somesimplistic correlates - a singlenumerical measure of neuronal

function that is meaningful. In­spite of very categorical attempts,the brain function called

'intelligence' has to date defied afoolproof and objective quan­tification. The allure of numbershas been irresistible and severalnumerical measures of intel­

ligence have been proposed. Oneof the earliest was worked out byPaul Broca, one of the greatestcraniologists of the earlier cen­tury. In the year 1861, on the basisof elaborate data, Paul Broca em-

·-- --. -- ------- - --- .... --

THE BRIGHTNESS MARKED 81

phatically concluded - "In general, the brain is larger inmature adults than in the elderly, in men than in women, ineminent men than in men of mediocre talent, in superior racesthan in inferior races ..... other things being equal there is aremarkable relationship between the development of intel­ligence and the volume of the brain". These were the conceptswhich led to biological determinism, a proposition with in­jurious social consequences. It was not long before loopholesin Paul Broca's interpretation were realised. Exceptions lik~the large volume of brains of criminals and the relativelysmaller volume of those of men of intellect dealt serious

blows to the foundation of craniometry. Though Broca'sschool of thought did not stand the test of time, it did muchto influence the intelligence tests of the next era.

The Director of the Psychology Laboratory at Sorbonne,Alfred BINET(1857-1911), keen to find a measure for intel­ligence started by retracing Paul Broca's foot-steps. Seekingto find a correlation between the head size and academic

performance, he conducted an exhaustive biometric analysisof school children but with little success. Even selective sam­

pling yielded insignificant differences between the brightstudents and the dull ones, a difference of about 3 to 4 mmon an average. IncoJ,lclusive craniometry made Binet changehis approach - he tried a psychological one this time. How­ever, the primary aim of his new study was to identify theslower ones at school, so as to help them out. Specific testswere devised to check the reasoning and comprehensionrelated to every day life. The tests were mixed ones, involvingsimple tasks. The results, expected to reflect the child's men­tal potential, could be read out as a single score. A youngstercould start off by performing a simple task and go ahead. Asthe tests became more complex" a 'mental age' could beassigned on the basis of the last task the child could success­fully perform. A comparison of the 'mental age' and theactual' chronological age' helped grade the child on 'Binet'sscale' of intelligence. An additional calculation gave the

82

624

21o

MIND MASTER

4o4

Test of scrambled letters

W

CHSIII000

L

MM0I!LEEN

~p~~t7~~(JOOQQ[)eJ

Test of novel items

Various types of intelligence tests

THE BRIGHTNESS MARKED 83

quotient that became the most popular measure of mentaltesting. As suggested by a German psychologist WilliamSTERN; the ratio of' mental' and 'chronological' age becamethe "intelligence quotient" (IQ) - a single figure repre­senting a complex brain function!

Initially the IQ was used with caution - as a measure toidentify and help improve the poor academic performers. Atotally new dimension was added to it when the scores of IQtests were professed to represent inherited, innate mentalabilities. Further, attempts were made to identify the so­called 'feeble minded' people with low IQ, who had inheritedit, probably as a single genetic characteristic. The leadingeugenetist H. GODDARD widely propagated these ideas.Popularising the IQtest at all academic levels, the professorof Stanford University Lewis M. TERMAN revised the test,calling it the :Stanford-Binet' Scale. However, an unhealthysocial trend in all the measurements had set in. Suggestionslike the elimination of those with very low IQ from normalsocial life were in the air, spelling doom for the so-called'feeble minded' people. The role of environment in intellec­tual maturation was undermined, especially after Sir Cyril L.BURT (1883-1971) claimed very high correlation between IQscores of identical twins, brought up in different environ­ments. It was later realised that the whole exercise of IQtesting, its implications and its supposedly genetic qualitywas based on extremely presumptuous arguments. From thevery beginning this mismeasure of human worth wasplagued by the personal biases of its founders, samplingerrors, ill-framed experiments of its protagonists and poorstatistical extrapolations by its supporters. As the criticalcontribution of environmental factors in the development ofhuman faculties came into focus, the fallacies of reading toomuch into IQ test scores became obvious. The IQ stormsubsided, after affecting many.

It is but natural that intelligence is difficult to measure-because in the first place, defining it is not easy. The Greeks

84 MIND MASTER

were the first to recognise certain aspects of human nature asspecial-those that make us think, reason, comprehend andhelp solve problems. CICERCO coined the term 'intelligence'to measure all these cognitive functions of the brain. In thelast century, William STERN, the German psychologistdefined intelligence as 'a general capacity of an individualconsciously ad,justing his thinking to new requirements. It isin general a mental adaptability to new problems andconditions'. On similar lines, recently, the Americanpsychologist David WECHSLER called intelligence 'theaggregate or global capacity of individual to act purposeful­ly, to think rationally and to deal effectively with hisenvironment'.

Horward GARDNER of the Harvard School of Education

defined intelligence a little more elaborately. He proposed atheory of multiple intelligence that envisaged a "relativelyautonomous intellectual competance" in an array of humanabilities. Identified as skills or talent, musical and bodily­kinesthetic competance are two such endowments. Bothinvolve complex motor and neuronal functions responsiblefor understanding. Thirdly, the mathematical ability, closelyrelated to creativity and logical reasoning is another specialtype of human intellect. A sense of space, an ability tovisltalize in three dimensions is another distinct human com­

petance. Embedded in the cultural ethos are more humanattributes. Gardner identified three of them as linguistic,interpersonal and intrapersonal intelligence. The eminentneurobiologists Karl POPPER (1902- ) from Germany andJohn C. ECCLES(1903- ) from England translated thisspectrum of intellectual functions of the human brain into anheirarchy of "W orIds" in which we live - simultaneously!

The first world in which we exist is limited by the physicaland organic structure of our brain. A fairly large part of thisworld has been traced. For example - one could identifythe part of the human brain involved in speech. Superim­posed on this 'world' is a second one - the one we exist in

THE BRIGHTNESS MARKED

Linguistic

Bodily kinesthetic

Interpersonal

Seven types of intelligence

Spatial

Intrapersonal

85

.---. --- - - .. -- ..

86 MIND MASTER

because of our percep­tions, memories, thoughts,emotions and imagina­tions. This is a personalworld full of subjectiveknowledge. What Gard­ner calls as spatial andmathematical ability or. _

KarlPopper skilled functions are John C. Eccles

probably part of thisworld. Eccles and Popper further proposed a third world, inwhich our knowledge is consolidated in a subjective sense.This world is built in a culture and has a characteristic scien­

tific, philosophical, historical and literary milieu around aperson in his environment. Linguistic, interpersonal and in­trapersonal intelligence proposed by Gardner would fall inthis world. A human personality seems to be moulded byinteraction of all the three worlds resulting in a combinationof all seven shades of intellectual development. The resultingunique, colourful personality can hardly be defined by asingle parameter. Intelligence, perceived as a multifaceted,some what transcedental quality of human brain, presentsneurobiologists with a new challenge of re-writing thesedefinitions in their own language of nerve nets and neuronalcurrents. The task is daunting as we are in a primitive stateofknowledge about ourselves. However, some attemps havebeen made by identifying some critical functions of the brainthat together give a certain intellectual capaci ty, no matter ofwhich of Gardner's type, no matter in which world of Popperand Eccles.

Comprehension of the situation one lands into, with thehelp of the sensory limb of the nervous system, has beenacknowledged as a primary intellectual neuronal function. Aconscious understanding, an acute awareness and an ap­propriate interpretation of all the signals sent in by the sen­sory organs can be said to be a mark of brightness.

THE BRIGHTNESS MARKED

Widespread areas of the brain; specially those of the cerebralcortex are actively involved in this process. Sub-divided intofunctionally specialised areas, the cortex is abusy station. Thevisual, auditory and somesthetic areas receive signals fromeyes, ears and skin respectively. These provide first handinformation of the surroundings. A trifle away, located at adistance from the primary sensory centres are the associationareas,. These are the areas that receive inputs from theprimary sensory areas. Here a higher level of neuronalprocessing takes place due to the integration of sensory in­formation~this qualitatively enriches an experience. Conse­quently, visuals acquire a texture, sounds acquire adimension and interureted with reference to each other, theprimary sensations become an intellectual exercise. Severalfacts of the environment get focused at the same time, result­ing in an overall understanding of the situation. Indeed, foran intelligent performance of the human mind it is obligatorythat sensory inputs are well understood!

The perception of a situation is incomplete unless thedimension of time is added on. A sense of time is a pre­requisite for an analysis of a situation. A sense of the past isstored as memories while that of the future is reflected in

planning and anticipating. In fact, the present can never beperceived in isolation since both, the past and the futureinfluence our perception and handling of a situation. The pastis codified into the data bank of the brain-the hippocampus.Data from this store are recalled, compared and contrastedwith the on-going experience. This evaluation with referenceto the past, qualitatively improves the picture of the present.Obviously, a fine memory, with a rich store of past experienceis a great asset. However, the recall should only be of ap­propriate memories! The thalamus, with its multiple connec­tions with various regions of the cortex, plays a critical rolein choosing out relevant data from the memory store. All thisintegrated, neuronal information converges on to a veryversatile region in the cortex - the Wernicke's area. Involved

88 MIND MASTER

A sense of the past is stored as memories while that of the futureis reflected in planning and anticipation

THE BRIGH1NESS MARKED 89

also with handling the knowledge oflanguage it is in this areathoughts precipitate, perceptions find expression and allneuronal information decoded and put into wprds. Findingcorrect words for communication is yet another intellectualachievement. The importance of lingual competence in theprocess of thinking was explained elegantly by AlbertEINSTEIN (1879-1955) -"We might be inclined to attributeto the act of thinking complete independence from languageif an individual formed or was able to form his conceptwithout verbal guidance of his environment; yet, most likely,the mental shape of an individual growing up under suchconditions would be very poor. Thus, we may conclude thatthe mental development of the individual and his way offorming concepts depend to a large degree upon language" .It is, therefore, hardly surprising that a blow to theWernicke's area has devastating effects on the thinkingability. To minimise confusion between the two hemispheresof the cortex, the Wernicke's area of one side alone - usuallythe left one in a right handed person - is functionally incharge of the thoughts. The ultimate destination of theprocessed signals, marching through the cortex is often'hippocampus' or 'amygdala' or both - the pair of struc­tures involved in storing thoughts till further recall. Wellbefore these destinations are arrived at, the mind has ac­quired a lot of 'common sense'!

The leap of human intellect ahead of time is an exclusivequality of our brain. Thinking with equal fluidity about timejust a few moments away and of time as an infinite enti ty, thehuman brain excels in imagining, anticipating and planning.The part of the brain somewhat responsible for these func­tions is a so-called' silent area' of the cerebral cortex. It is the

not so silent, prefrontal lobe, lying anterior to the frontalregion. It was thought to be quiescent as its disfunctionseemed to cause no gross effect on the survival of the person,but very subtle intellectual faculties were lost. An awarenessof consequences that the actions of the present can have with

90

- ..- ..._-. ------.-. --- .-- .... --- ... --- ---------------

MIND MASTER

the passage of time, is missing. An utopian bliss sets in forsuch a person - as he is free of worries. This pathologicalexemption from worry, however, hardly compensates for thelosses. The most beautiful capacity of the human mind, ofabstraction and elaborate mathematical computation is lost.Bits of information that need to be held in the mind as short

term memory for sequential calculations slip out - leavingthe brain incapable of solving problems by logical reasoning.The prefrontal region is responsible for ded uctive logic - thetype Sherlock Holmes used to solve intricate cases. A doctorarriving at a diagnosis, and a scientist analysing his resultsuse the same faculty of logical arguments. Reason fails witha person with damaged prefrontal lobe. Left to the control ofWernicke's area alone, the mind of such a person is stormedwith illogical, extreme reactions. Emotions play havoc in theabsence of' reason' to hold them back. The result is disjointedbehaviour, with sudden outbursts of rage or dispropor­tionate levels of happiness. It may not be too presumptuousto say that the unreasonable fury of rage, dislike or fear weexperience at times is due to our perceptions escaping thelogical constraints of our prefrontal area! To have thoughtswell under control of reason and a corresponding soberbehaviour is probably another halmark of the intellect.

In the dull glow of commonplace intelligence, brightsparks of original creativity often light up the world. To thinkthat the same anatomical structures that contribute to' com­

mon sense' and 'simple abstractions', support works of in­credible originality might appear paradoxical. However, theimagination is known to interfere with general intellectualactivity - (so much for absent minded Professors!). Yet,conceiving a new idea is not enough, picking out a good oneis a sign of intellectual jurisprudence. Moreover, originalityis often not spontaneous - a trigger from memory isobligatory. At times the crucial clues come from the culturalenvironment. What really stimulates the creative people andhow is yet another loose end of the story.

THE BRIGHTNESS MARKED 91

It is the unanswered questions that makes neuroscienceschallenging. Our inability to find an outright measure for thecomplex neuronal function called 'intelligence' makes theissue more interesting. Human ip.telligence does have agenetic component in the form of a basic architecture of theneuronal network. How~ver, for this basic structure to befunctionally exploited in full and for the genetic potential tobe totally realised, the environment should playapredominent role. Underestimating the role of environmentin moulding the individual human intellect is likely tofrustrate any attempt at judging this human faculty. To givea common questionaire to people in different environmentsin order to judge a subjective faculty like intelligence, reallyyields little. The obligations of scores, marks, grades are onlyutilitarian yardsticks. Human qualities can bloom far beyondsuch mundane measures - and can scale worlds of percep­tion and culture as never before.

ACreative

Chemistry

N vivid yellow and blue, arage of colours poured ontothe canvas. The creative mind

of the genius emptied itself in"Wheatfield with Crows" - the

last work of the great Dutchpainter Vincent van Gogh (1853­1890). Soon after he shot himself.Struggling to keep his mind frominsanity, van Gogh painted withwildly fluctuating moods. Someof his work mirrors his utter

despair. Reflections of the tran­quil periods in his life are alsoseen in some. Towards the end his

desperation, as he fought topreserve the integrity of his mind,had taken the form of vibrant can­vases. Even in the worst of his

time the grip of creativity seemsto have remained as steady asever. The brain cells that had

taken him to his artistic heights,however, failed him in the end.The chemicals within probablyplayed havoc - forcing him tofinish off everything abruptly.The year was 1890 and little wasknown about the chemicals thatruled the brain. We have come a

long way since. With informationaccumulating about thechemistry of the normal function­ing of brain, the torments of dis­turbed individuals can be well

appreciated. Psychosis, oftenseen so closely associated with

A CREATIVE CHEMISTRY 93

van Gogh (inset) and a part of hislast painting "Wheatfield with Crows"

94 MIND MASTER

extremes of creativity, can also be understood a little more.The mentally ill are not as lonely as before.

The chemical story of the brain function has taken years tobe put together. Apart from the biological molecules thatmake up the gross architecture of the brain, the moleculesthat make it functionally dynamic are the neurotransmittersand the neuromodulators. Early information was availablefrom work done on the physiology of nerve stimulation. Anextract of adrenal gland was seen to evoke a change in theheart beats exactly as a stimulation of the concerned nerveswould. John N. Langley and his team devised ingeniousexperiments to demonstrate the presence of a chemical in­volved in the neuronal function. Two decades later Otto

LOWI (1873-1961) from Germany confirmed the presence ofacetylcholine, a substance from the vagus nerve that in­hibited the heart. Extensive evidence of the role of chemicals

at the junction of two neurons, the synapse, was presentedby Sir Henry DALE (1875-1968) and his coworkers in 1935.Sir Dale made a suggestion that remained a guideline foryears to come and developed into a 'law' with profoundimplications. He postulated that if a type of messengermolecule, the neurotransmitter, is present at one synaptic endof a neuron, all other ends would probably have the sametransmitter substance. This seemed to be so in most of the

cases, until recently. Several instances of co-existence of dif­ferent neuroactive substances at the same synaptic terminushave now been reported giving a new direction to our under­standing of information processing by neurons.

Though the presence of neurotransmitters and theneuromodulators was known for quite some time, beingsmall in size and quantity, they remained elusive, difficult toisolate and characterise. It was, therefore, a majorbreakthrough when Victor P. WHm AKER of the Universityof Cambridge and Eduardo De ROBERTIS of the Universityof Buenos Aires isolated' synaptosomes' from the brain tis­sue. Found within the nerve cells, these were tiny bags pack-

A CREATIVE CHEMISTRY 95

ed with neurotransmitters poised to be released. Gettingthese bags out into test-tubes accelerated in vitro studies ontransmitters. Another scientific milestone was the develop­ment of the immunohistochemical techniques. Antibodiesproduced against a neurotransmitter could be tagged with acolouring reagent and when atissue section was flooded withthese tagged antibodies, colour could be seen wherever theantibodies held onto the transmitter molecule. This veryspecific visualisation of1he transmitters permitted a surveyof their distribution in various parts of the brain. A neuronalpathway could be traced using a chemical. Over the years anew map of the brain anatomy has unfolded - it is thechemical one this time. The map is by no means complete asyet!

"Light seems intense in all that is seen with the inwardeye .... With this intensification of light goes a tremendousintensification of colour .... Finally there is intensification ofwhat I call intrinsic significance. That which is seen eitherwith eyes closed or open, is felt to have a profound meaning."This is the description of a visionary experience induced bya hallucinogen 'Mescaline' and recorded not by anyneurotic but by a conscious experimenter, a well-knownliterary figure - Aldous HUXLEY (1894-1963). Mescalinewas of special interest, as it closely resembled theneurotransmitters - epinephrine and dopamine. So closewas the molecular likeness that it practically mimicked thenatural chemicals. Both dopamine and epinephrine areknown to be in charge of our moods. Epinephrine is respon­sible for attention, consciousness, wakefulness and for sleepwith dreams. The brain stem lodges a group of neurons richin epinephrine. Projections from this locus stretch out to thefore-brain, cerebellum and to the hypothalamus. The mid­brain, on the other hand, has neurons rich in dopamine withtracts leading again to the fore-brain - that makes it respon­sible for movements too. Another related transmitter is

serotonin. Distributed in various regions of the brain it

A CREATIVE CHEMISTRY 97

mediates sensations of pain right down through the spinalcord. It is also the one that makes us aware of day and night,helping the body to set up the routine cyde of keeping awakeand sleeping. Insomnia is often a result of disturbance ofserotonin function. Interestingly, the most potent hal­lucinogen, lysergic acid diethylamide (LSD) is a moleculethat almost looks like the serotonin molecule. The amines ­

dopamine, epinephrine and their twin norepinephrine asalso serotonin run errands throughout the brain. Anothermember of the family of amines is acetylcholine, the moleculein charge of peripheral communication. It is known to playarole in the brain as well. The amines, however, are not theonly ones that govern the neuronal functionary, there areseveral other participants.

In 1950, the Journal of Biological Chemistry published twoindependent reports by Jorge AW APARA and EugeneROBERTS. Both reported the presence of the special aminoacid, the gamma amino butyric acid (GABA) in the brain.Twenty years later, the final confirmation of GABA being alegitimate neurotransmitter also came from Roberts' team.Later immunohistochemical techniques were used todemonstrate the presence of glutamic acid decarboxylase, theenzyme responsible for synthesising GABA in special cells ofthe cerebellum, the 'Purkinje cell'. Produced exdusively inthe brain, the content of the enzyme in the brain is 200 to 1000times more than that of the amines. Widely distributed invarious regions of the central nervous system, it has a verystrategic function to perform. It runs down the incomingsignals, thereby blocking the flow of transmission. Itsobstructive presence at the synaptic junction ensures a selec­tive processing of the input. Lodged in the inhibitory inter­neurons all over the brain, it is an ideal guard againstexcesses. It is hardly surprising, therefore, that increasedeffectiveness of GABA would control hyperactivity ofneurons and help relax. The most popular anti-anxiety drug'Diazepam' (valium) seems to be working on same principle

98

Joo {[

MIND MASTER

Blocking of neurotransmitters does not allow signals to pass

- increasing the effectiveness of GABA in neuronal informa­tion control. Diazepam seems to have an independent set ofreceptors for itself in the brain. The possible role of thesereceptors, is difficult to explain, unless a naturally occurringrelaxant, structurally close to diazepam, is around.

Released in measured quota with every wave of the nervestimulation, the neurotransmitters bathe the synaptic cleft­the gap between the two communicating neurons. Themembrane of the immediately next neuron receives thesemolecules at specific 'receptor' sites. The interlocking of thetransmitter molecule and its corresponding receiving

A CREATIVE CHEMISTRY 99

partner, the 'receptor' triggers an alteration in the per­meability of the cell membrane. The opportune ions, justwaiting for such a change, reshuffle themselves building upstep by step 'synaptic potentials'. For speedy transmission,the receptors of neurotransmitters need to be alert. Some areso, because they are in direct contact with the ionic channels.A mere binding of a transmitter to such a receptor makes itchange its dimensions, resulting in opening up of the as­sociated ionic gates. On the other hand, some receptormolecules are not in much hurry to forward the information.They involve a 'second messenger' - usually the purinederivatives - the cyclic adenosine monophosphate (cAMP).Binding of the neurotransmitter to its receptor stimulates anenzyme which is close to it, on the cell membrane itself. Thisenzyme, the adenyl cyclase converts adinosine triphosphate(ATP) to cyclic adinosine monophosphate (cAMP). ThecAMP is an efficient messenger molecule. Another similaryactivated messenger molecule is cyclic guanosine monophos­phate (cGMP). Both these molecule, can in turn activate a hostof enzymes - the protein kinases. As their names suggestthese enzymes act on proteins. They do so and bring aboutalterations in special proteins that are involved in openingand closing of ionic channels. These alterations open theflood gates1 The permeability of the membrane to sodium,potassium and also to calcium changes. The net result is anincrease of positive charges inside the cell, making it a littleless negative. This 'depolarization' is called "excitatory postsynaptic potention" (EPSP) and can be recorded usingmicroelectrodes in the neuron receiving the neurotransmit­ter. However, potentials are not always excitatory, they canbe inhibitory as well! And "inhibitory post synaptic potential"develops when the permeability to potassium and chlorideions is altered. The potassium ions leach out and/orchloride ions move in, making the interior of the cell stillmore negative. In other words, there is a further polariza­tion, the potential across the membrane becomes a little morenegative. Under this condition, a little extra effort is required to

100 MIND MASTER

stimulate the neuron, to bring about the depolarization thatwould fire it. This is a trick played at the synaptic junctionto hold back the signals or to tone them down.

The cell body of the neuron, receiving inputs through anumber of synapses is forever busy - it does a mini com­putation like a computer. Excitatory and inhibitory signalsare integrated as they arrive and a net change in membranepotential is communicated to the beginning of the axon. Ifthis alteration in potential is beyond the threshold requiredby the neuron to fire, it does so and off goes the impulse­down the axon, jumping over the myelin sheath right toanother synapse! The ionic drama is enacted allover again!The two types of receptors - the ones that are directlyassociated with channel proteins and those which need thehelp of a second messenger, are strategically distributedthroughout the nervous system. In the brain, many receptorsare of the latter type which requires a second messengersystem as the decisions need to be less hasty. In addition, evena weak interaction between the transmitter and the receptormay generate several second messenger molecules, therebyamplifying the original signal and eliciting a. sustainedresponse. The most widely used drug 'caffeine', present incoffee and tea, is known to inhibit the enzyme that breaksdown the cAMP after its job is done. This effectively allowsan accumulation of the message and consequently aprolonged stimulation of the nerves. That's what gives us apep after the drink! .

I

Recently, Stewart HENDRY and his colleagues reportedan unusual observation. Certain neurons of the cerebral cor­

tex had more than one neuroactive substance at their synapse- a situation where the Dale's law failed! Neuropeptideswere reported to coexist with GABA. Presence of a peptidealong with an inhibitory neurotransmitter is likely to provideimportant clues about the chemical processing 'Jf informationin the cortex. Though what exact role this particularneuropeptide plays is not known, there are a lot of other

A CREATIVE CHEMISTRY 101

things we now about neuropeptides. An incidental observa­tion led to the discovery that peptides too were involved inthe nerve function. The narcotic drug derived from the opiumpoppy, morphine, was seen to bind certain specific regionsof the brain. These regions of the brain had special receivingstructures for opium - the opiate receptors. The opiatereceptors are richly scattered in the part of the brain respon­sible for integrating perceptions, for pain and for hallucina-·tion. John HUGHES and Hans W. KOSTERLITZ in 1975,came up with ~o naturally occurring chemicals that couldalso bind the opiate receptors. They called them theenkephalins, meaning 'from the brain'. A striking molecularresemblance was seen between these and morphine. Later,other morphine-like molecules - the endorphins were iso­lated. Both enkephalins and endorphins are closely linkedwith the emotional integration of perception and with thepain system. Formed of small chains of amino acids, severalother neuroactive peptides, however, do not qualify strictlyas neurotransmitters. They appear to modulate complexneuronal functions, very apparently causing behaviouralresponses. Moreover, they are not restricted to the neuronalsystem but may have related functions to perform in otherorgan systems. Peptides like neurotensin and enkephalinsare there in the gut as well. Neuropeptides in the brain appearto belong to a broader category of chemicals - moleculesinvolved in cellular communications. Unlike neurotransmit­

ters, they have a multiplicity of functions to perform in thebody - one of them being modulation of the neuronal func­tion! Such modulatory molecules, coexisting with transmit­ters, probably act as fine tuners, ensuring very preciseprocessing of information. Their presence in the corticalneuron suggests a critical manipulation of neuronal informa­tion - one that results in the highly sophisticated functionsof our brain.

As we know more and more about the chemistry of thebrain, some aspects that can be reflected upon corne into

102 MIND MASTER

I think his enkephalin levels are rather low!

A CREATIVE CHEMISTRY

~.- -

103

Contrary to natural chemicals a trip with mimicksis a fruitless journey ending in a stupor

focus. Our preoccupations with drugs, ever since any formof culture developed, was probably inevitable. Hal­lucinogens, intoxicants, antidepressants, pain relievers are all

104 MIND MASTER

there, right within us. 'Plese mimicks appear in nature inabundance and interestingly, are distributed widely in theplant kingdom; one wonders what these molecules do inplants! The natural chemicals and the mimicks have a fairamount of structural overlap - the difference is small- yetit is the difference between the pleasures of creativity andhell. An emotional upsurge, added onto a vision and percep­tions of transcendental quality, all caused by the chemicalswithin, would result in creations like that of van Gogh'spaintings. The chemical balance tripping a trifle at times,alienating creative people from reality, may be an associatedmisadventure! On the other hand, a trip with mimicks, allcomplete with a visionary experience, is a fruitless journeyending in a stupor. Molecules, so similar, result in inducingbehaviours which are ultimately so different.

Creativity, a phenomenon manifested exclusively by thehuman brain has been an enigma to neurobiologists. Anemotionally intense, sensitive disposition and extraordinaryperceptual qualities are often seen associated with creativeand artistic abilities. This suggests that creativity probablyhas its roots in the chemical anatomy of our brain. We have,as yet, no clues as to what concoction of chemicals andanatomical structures of the brain and of environmental fac­

tors would come up with the best in each of us. What makesa blooming creative personality that fully exploits the geneticpotential, is still not clear. Educationists now believe thatcreativity can be taught, atleast creative thinking can be.Would that be close to manipulation of the chemicals within?

Not Yetthe

Last Word

ITILE more than ten yearsago, David H. Hubel,Professor of Neurobiology

at Harvard Medical School com­

mented "How long it will bebefore one is able to say that thebrain or the mind is in broad out­

line understood is anyone's gliess.As late as in 1950, anyone whopredicted that in 10years the mainprocesses that underlie life wouldbe understood would have been

regarded as optimistic if notfoolish; and yet that came to pass.I think it will take a lot longer than10 years to understand the brain,simply because it is such a manyfaceted thing - a box brimful ofingenious solutions to a hugenumber of problems". There is aschool of thought, however, whowould like to suggest that we mayreall y never be able to knoweverything about our brain. Trueto the famous mathematicaltheorem of Godel, "that a mathe­matical system cannot be com­pletely self-descriptive" - a lotabout the brain may remainbeyond our reach. Not everybodyconforms to this view though; andso there are explorations going onand are likely to go on for severalyears to come.

Todate, we have a fair pictureof the fundamental units that

106 MIND MASTER

make up the brain, of the way molecules carry messages, thecode in which the information is ciphered and a generalisedidea of how these units are organised into functional net­works. We also have an insight, to some extent, how certainsensory information can be perceived and stored. Enormousdata have accumulated over the years. Like the blind mengroping and trying to understand the elephant, with eachnew technical advancement, a different picture of the cellinteractions gets into focus. The "putting of the 'elephant'together" has been achieved to a great extent. However, thelast words are yet unsaid. One major lacuna we are not yetable to fill, is to understand the role of the genetic material inall these functions. What part do hereditary factors play inintelligence, innovations and behaviour? There is no doubtthat environment has a major contribution to make whilegenes too make their presence felt. Genetics of the nervoussystem has been a tricky field to work in - especially as ithas such intense social implications. For that matter everyaspect of neurobiology is socially relevant. At this juncturewe know a lot and we don't know a lot about our brain. That

is an interesting situation to be in - as there is a lot that canbe done!

Wherever the increasing knowledge about our brain takesus, there are some unusual aspects of our behavioural patternthat are likely to haunt us. We as a race, with all the intellec­tual quality that the neocortex has endowed us with, have aliability. That is our susceptibility to prejudices. The trap ofpreformed ideas - often passed on to us through generations-limits the freedom of our brain quite unknowingly. OttoKLINEBERG of the Centre for Study of Intergroup Relationsin Paris has some interesting observations to make in thisconnection. He points out several ways hl" which we con­sciously trick ourselves to establish what we believe is right.'Selective inattention' is one way of doing so. Just as selectiveattention helps retention of important information, selectiveinattention works in reverse - neither we notice nor

NOT YET THE LAST WORD 107

remember what does not best suit our preformed ideas.'Distortion of imagery' is a form of wishful thinking thathelps us preserve only what we want to. The human mindcan 'shrug off' what it does not understand - reducing theimportance of a particular perception in the process ofthought. We 'reinterpret observations' so as to make con­clusions that confirm the bias. All these conscious and uncon­

sCious ways of accommodating our beliefs give a rigidity toour thoughts and to our'j~dgement. That the possibility ofhuman error is enormous is a fact that needs to be acceptedand the world needs to be understood with an intelligentscepticism. Unless we do so, the neocortex on which evolu­tion has put a premium will no longer be of any selectivevalue. With a highly developed capacity for self destructionand forever on the brink of war, the human race needshumility and circumspect wisdom. Moreover, mere reasonmay not be enough/reasonableness' with an element ofaltruism may be the only pattern of behaviour that will helpus survive.

Glossary

Acoustic: Related to the sense of hearing.

Amines: Organic compounds of ammonia in which one ormore hydrogen atoms are replaced by organic groups.Amino acids: Organic acids containing the amino group.These are the buildings blocks of proteins.

Amygdala: An almond -shaped structure consisting of a largegroup of neurons, located deep inside each temporal lobe ofthe brain, that functions closely with the hypothalamus andis believed to help control behaviour.

Angular gyrus: A fold in the surface of the cerebrum respon­sible for information integration.Anterior commissure: A bundle of nerve fibres connectingfront regions of the two hemispheres of the brain.Anthropology: The scientific study of human beings espe­cially their social, cultural and physiological development.Antibodies: Protein mDlecules synthesized by body's im­mune system. They defend the body against infection.Auditory: Pertaining to the ear or the sense of hearing ..

Biometrics: Statistical study of living organisms and theirvariations.

Body cavity: The space inside the body in which the organslike heart, lungs, liver~etc. are located.Cerebellum: The lowermost part at the back of the brain,concerned with coordination of complex muscular move­ments.

Chemoreceptor: A sensory nerve-ending capable of receiv­ing chemical stimulus.Chip: A tiny flat piece of silicon crystal containing thousandsof electronic components such as transistors, capacitors, etc.

Corpus callosum: A transverse band of nerve fibres whichjoins the two hemispheres of the brain and makes themfunction as a single unit.

GLOSSARY 109

Cosmologist: One who studies the origin, nature, structureand evolution of the universe.

Craniologist: One who makes scientific study of skulls.

Craniometry: The science of the measurement of thecranium, or skull.

Cytologist: One who studies the structure and functions ofcells.

Cytoskeleton: The structural elements within the cell.

Enzyme: A protein which catalyses biochemical reactions.

Frontal: Pertaining to the front of the head above the eyes.

Ganglia: Small solid masses of nervous tissue out side the centralnervous system made up of cell bodies (singular ganglion).

Ganglionic: Pertaining to ganglion.

Hallucinogen: A drug or chemical under the influence ofwhich one perceivs sensations without any external stimulusand which are not real.

Hamster: A rat-like rodent bred and used extensively as aexperimental laboratory animal.

Hippocampus: An elongated structure in the centre of thebrain believed to be associated with memory and emotions.

Hominid: A member of a human or human-like specieswhich can stand upright.

Hydra: A small freshwater backbone-less animal belongingto phylum Cnidaria.

In vitro: Biological experiments carried out in a test tube orany laboratory glassware.

Insomnia: A persistent inability to get sleep.

Intra-cranial space: The space within the skull.Invertebrates: Animals without backbones.

Kinesthetic: Pertaining to the sense by which one is aware ofthe position and movement of various body parts.

110 MIND MASTER

Ligaments: Elastic fibrous tissue joining two or more bonesor cartilages.

Lipid: Any oil, fat or similar water-insoluble substance foundin living tissue.

Mammals: Animals with backbones which possess hair andsuckle their young.

Mechanoreceptor: A sense organ specialized to respond tomechanical stimuli such as pressure on bending.

Metabolism: The sum-total of the chemical and physicalchanges constantly taking place in a living organism.

Neuromodulator: Any of a class of chemicals found in thebrain which affect the transmission of nerve signals.

Neuron: A nerve cell.

New mantle: A region of the brain responsible for speechproduction, thinking, etc.

Occipital cortex: The back part of the cortex.

Osmotic pressure: The pressure which must be applied to asolution separated by a semi-permeable membrane frompure solvent to prevent the passage of the solvent throughthe membrane.

Peptides: Substances resulting from the breakdown ofproteins and made up of two or more amino acids.

Phoneme: A unit of significant sound in a given language.

Photoreceptor: A sensory cell that can detect light.

Phrenologist: One who studies mental abilities and per­sonality characteristics from the shape of a person'sskull.

Pitch: The property of a sound that characterises its highnessor lowness to an observer.

Plasticity: Degree to which the central nervous system canchange in response to learning or injury.

GLOSSARY 111

Pons; The structure connecting mid-brain with medullaoblongata.

Precursor: Any substance that can be converted into anotherspecific substance by simple chemical or enzymaticprocesses.

Primates: Animals of the highest order of mammals whichinclude humans, apes, and monkeys.

Purine: A nitrogen-containing constituent of nucleic acids.

Radioactive: Any of the elements that undergo spontaneousdisintegration with the emission of charged particles andhigh- energy radiati~n.

Receptor: A specialized site on or in a cell to which specificmolecules such as those of a drug, hormone, etc. can selec­tively bind.

Sea horse: A bony fish with a horse-like head.

Semantics: The meaning attached to words or symbols.

Sensorium: The entire nervous system including the senseorgans.

Somasthetic: Pertaining to the consciousness of having abody.

Spectrogram: Photographic record of a spectrum.

Stria: A strand of longitudinal fibres in the brain.

Synapse: The region where one nerve cell makes functionalcontact with another.

Tactile: Pertaining to touch.

Temporal lobe: The part of the brain situated under thetemples on either side of the head.

Thermoreceptor: A nerve-ending that can sense heat.

Tissue: A group of cells of similar type performing a par­ticular function.