The Observer is the Observed: Towards Integrating Pain Phenomenology and Third-Person Methods in the...

The Observer is the Observed: Towards Integrating Pain Phenomenology and Third-Person Methods

in the Scientific Study of Pain

Simon van RysewykTaiwan National Science Council

Postdoctoral FellowTaipei Medical University

my focus todaya puzzle for pain science about introspectionpain studies in which researcher-subjects use introspectionexperiential method that integrates first and third-person methods to study pain

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a seeming puzzle for pain science

1 experiences seem knowable via introspection

2 introspection is subjective3 science is intersubjective∴ experiences cannot be a scientific object

(experiential science is not objective)

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like vision, pain has an object of perception (tissue damage)unlike vision, pain itself is an experience only knowable by introspection‘An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage’ (IASP)

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1 pain seems knowable via introspection2 introspection is subjective3 science is intersubjective∴ pain cannot be a scientific object (pain science is not objective)

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the puzzle’s impact on pain science

conclusion false – pain science studies the brainpain experience and brain activity must be distinct (cartesian dualism)pain science studies brain correlates of pain, not pain itself

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dualism is true of pain science

cartesian dualism implies that the subject matter of pain is brain activity related to painpain science is committed to introspectionpain-neuroimaging was established by robust correlation of neuroimages with pain self-reportcartesian dualism and pain science are historically consistent

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dualism is true of pain science

metaphysical dualism is not convincing

pain science can assert epistemological dualism and mind-brain identity theoryidentity is advantageous: brain activity is identical to pain without revealing complex physical features of the brain

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two scientific uses of introspection

researcher-subject verbal/written reportnon-researcher-subject verbal/written reportintuitive notion of introspection:inner perception yielding knowledge of immediate personal statesintersubjectively available to researcherstaken to indicate sensory qualities

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researcher-subjects: double pain

first and second pain results from a sudden noxious stimulus to a distal part of the body0.5 to 1.5 second delay between the two pains impulses in thinly myelinated A axons (6–30 meters/sec) travel much faster than those in C axons (0.5–1.5 meters/sec)

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Lewis & Pochin 1938independently mapped body regions wherein they introspected double pain near the elbow but not the lower trunk although both sites are about the same distance from the brainC fibers that supply the trunk have a short conduction distance to the spinal cord


Lewis & Pochin 1938C fibers that supply the skin near the elbow have a long conduction distanceonce these C fibers enter the spinal cord, they synapse on A neuronsdifferences in peripheral conduction distance and time mean that double pain can be discriminated at the elbow but not the trunk



Landau & Bishop 1953first pain sharp or stinging, well localized, and brief (A fibers)second pain diffuse, less well localized, dull, aching, throbbing, burning (C fibers)second pain longer lasting than first pain, vague unpleasantnessSimon van Rysewyk 14


1.the results were obtained through researchers introspecting their own pain

2.observations about specific pain experiences

3.the observations have been integrated into our knowledge of pain

4.the observations have been replicated in studies using standard experimental designs and methods


relating introspection and brain activity to pain sensation and emotion

Rainville et al. 1997subjects rated pain sensation intensity and pain unpleasantness of immersion of the left hand in a 47° C water bath for 60 s


condition

hypnotic suggestion

sensation

1 ↑ pain unpleasantness no

change2 ↓ pain

unpleasantness

Rainville et al. 1997↑ unpleasantness increased magnitudes of pain-unpleasantness ratings and neural activity in ACC (area 24)no change in ACC for ↓ unpleasantnessno change in S1 activity and magnitude ratings of pain sensation intensity in both conditions


Rainville et al. 1997


Hofbauer et al. 2001


subjects rated pain sensation intensity and pain unpleasantness of immersion of the left hand in a 47° C water bath for 60 scondit

ionhypnotic suggestion

unpleasantness

1 ↑ sensation intensity

no change2 ↓ sensation

intensity

Hofbauer et al. 2001↑ intensity increased magnitudes of pain-intensity ratings and neural activity in S1no change in S1 for ↓ intensityno change in ACC activity and magnitude ratings of pain unpleasantness in both conditions


the significance of brain-pain phenomenology parallels

changes in experience and brain activity cannot be predicted only by stimulus propertieschanges in experience and brain activity can be explained by analysis of experience and brain activitythe neural activity sufficient for a given pain quality of pain does not prove it exists within one brain region


an experiential approach to pain

Barrell & Barrell 1975, Price & Barrell 1980


experimental tasks

phase

identify common factors within pain experiences

horizontal (first-person)

‘phenomenal structure’

identify common factor interrelationshipsidentify common factor-brain relationships

vertical (third-person)

‘brain structure’

horizontal phase


horizontal phase stages experimental subjects

1 question and observe

researcher-subjects

2 describe from a first-person perspective

3 find common factors and their interrelationships

4 use psychophysical methods to test generality and functional relationships between common factors

non-researcher-subjects

horizontal phase1.questioning and observing ‘What is it like to experience the unpleasantness of laboratory pain, such as immersion of the hand in a heated water bath?’how of pain (sensations, thoughts, feelings)

not why pain occurs (stimulus conditions)‘passive attention’, ‘being with pain’, immediate retrospective attention


horizontal phase2.describing pain from the first-personverbal/written reports of immediate

pain:‘My hand was immersed in a 47° C water bath when intense burning and throbbing occurred in my hand. Feel bothered by this and distressed. Is it going to get stronger? Concern. Hope my hand isn't going to be scalded’


horizontal phase3.finding common factors and

interrelationships‘phenomenological reduction’‘Is it going to get stronger? Concern. I hope my hand isn't going to be scalded” can reduce to‘I think and feel concern for future consequences related to this pain’


horizontal phase‘Feel bothered by this and distressed’

can reduce to‘I have a feeling of intrusion related to this pain’


horizontal phasedefinitional hypotheses: experiential factors commonly present during a pain-typefunctional hypotheses: common factor interrelationships


horizontal phasesample definitional hypotheses:1. an intense burning throbbing

sensation in the hand 2. an experienced intrusion or

threat associated with this sensation

3. a feeling of unpleasantness associated with this felt intrusion or threat


horizontal phasewhen the factors of intrusion or threat are present, there is a felt sense of pain

felt sense of pain is pain-aversionpain-aversion seems about felt bodily integrity


horizontal phasesample functional hypotheses:1.felt unpleasantness should

increase as a function of experienced intrusion or threat

2.experienced intrusion should increase as a function of the intensity of burning, throbbing sensation


horizontal phase4.applying psychophysical methodscontrolled observation of ratings of experiential factors (pain aversion) or sub-factors (concern)rating scale methods (ratio scales)subjects are not researchers


vertical phasecorrelate horizontal results with brain activity to establish possible causal relationshipspatterns of cerebral cortical activity that co-vary with different factors of pain could be identified


future questionscan less well-known introspective methods be used in the study of pain?are there experiential and neural similarities and differences between sub-types of acute and chronic pain?can there be a ‘neural signature’ of pain?


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