First-Person Neuroscience of Pain: Puzzles, Methods and Data

First-Person Neuroscience of Pain: Puzzles, Methods and Data

Simon Peter van RysewykGraduate Institute of Medical Humanities,

Taipei Medical University Brain and Consciousness Research Center,

Taipei Medical University-Shuang Ho Hospital

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my focus today

a puzzle about introspection and the limits of pain science

researcher-subjects

“experiential-phenomenological method”

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a seeming puzzle for pain science

P1 pains seem knowable via introspection

P2 introspection is subjective

P3 science is intersubjective

∴ pains cannot be a scientific object

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a seeming puzzle for pain science

P1 experiences seem knowable via introspection

introspection is a way of learning about one's own ongoing, or very recently past, experiences

targets conscious experiences, beliefs, intentions

produces beliefs, judgments, knowledge

requires proximity in time

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a seeming puzzle for pain science

P2 introspection is subjective

I have a uniquely privileged position about my experiences that no one else can have

I can directly and immediately access my own experiences in a way you cannot

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a seeming puzzle for pain science

P3 science is intersubjective

no one is epistemically privileged with regard to gathering evidence about the object of a study

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a seeming puzzle for pain science

P1 experiences seem knowable via introspection

P2 introspection is subjective

P3 science is intersubjective

∴ experiences cannot be a scientific object

∴ experiences are non-physical

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a seeming puzzle for pain science

P1 pains seem knowable via introspection

P2 introspection is subjective

P3 science is intersubjective

∴ pains cannot be a scientific object

∴ pains are non-physical

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cartesian dualism

PAIN begins in the PNSascends in specific pathwaysends in a specific brain centerintrospection of pain by the non-physical “soul”

Rene DescartesTreatise of man(1662)

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property dualism

imagine you are blind and you know all physical facts about vision

you have neurosurgery which enables you to see

you know all physical facts about vision, but on seeing for the first time you learn a new fact

the fact you learn is non-physical: what it is like to see

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understanding the seeming puzzle

“pain cannot be a scientific object”?

false – pain science objectively studies the brain

pain dualist: does pain science study pain itself or the brain correlates of pain?

pain depends on brain activity, but experiences of pain are only knowable via subjective introspection

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understanding the seeming puzzle

∴ pain experience and brain activity are distinct

pain science studies brain correlates of pain, not pain itself (“what it is like”)

“pain cannot be a scientific object”

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understanding the seeming puzzle

“pain science studies brain correlates of pain, not pain itself”

not quite right – the object of pain science is brain activity as related to introspected pain

pain psychophysics and neuroimaging rely on introspective report

animal studies await introspective confirmation

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challenging property dualism

“pain science cannot know what it is like to have a pain”

scientific explanations of experiences do not cause the experiences to occur (e.g., to feel pain)

if I learn all physical facts about pregnancy, would I thereby become pregnant?

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introspection might be physical

what science knows about experience may prove to be identical with what we know via introspection – specific brain activity

there are not two distinct activities (cartesian dualism)

there is only one kind of activity: brain activity with only physical properties

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introspection might be physical

direct introspection is beneficial for survival

introspection accesses brain activity in a direct way without telling us what the complex physical properties of such brain activity are

neuroscience tells us what those physical properties are

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introspection might be physical

we have color experiences without knowing what the physical surface properties are

color neuroscience tells us what the physical surface properties

our visual system responds to such physically complex properties without informing us about their properties: we simply perceive colors

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epistemological dualism of pain

replace cartesian dualism of pain with epistemological dualism of pain

two forms of access to one and the same phenomena – to the brain activity underlying pain experiences

∴ pains are physical

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summary

first- and third-person access to pain is essential in pain science and historical fact

dualism is consistent with pain science, but epistemological dualism of pain is preferred

epistemological dualism does not entail cartesian dualism

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two scientific uses of introspection

non-researcher-subject report (verbal/written)researcher-subject report (verbal/written)

double-paincatastrophizing and sensitization

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double pain

first and second pain results from a sudden noxious stimulus to a distal part of the body

0.5 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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double pain

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double pain

Lewis & Pochin 1938

independently mapped body regions wherein they introspected double pain

double pain near the elbow but not the lower trunk although both sites are about the same distance from the brain

C fibers that supply the trunk have a short conduction distance to the spinal cord

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Lewis & Pochin 1938

C fibers that supply the skin near the elbow have a long conduction distance

once these C fibers enter the spinal cord, they synapse on A neurons

differences in peripheral conduction distance and time mean that double pain can be discriminated at the elbow but not the trunk

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double pain

Landau & Bishop 1953

first 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 unpleasantness

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catastrophizing and sensitization

von Baeyer 2014

“When I walked on my treadmill for progressively shorter periods of time, a powerful aversive sensation would build up in the soles of my feet. I would rate the pain intensity at 3/10 and the unpleasantness at 8/10. The pain would stop a few minutes after I stopped walking on the treadmill, but would return quicker and stronger each time I resumed … the problem never occurred during ordinary walking.”

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von Baeyer 2014

“I told myself, ‘I wasted $1200. I'll never be able to use this treadmill. I'll have to go back to sitting at a desk. So much for my fitness plan,’ and similar discouraged thoughts. When I did attempt to walk on the treadmill while working, I could not concentrate on the work at all: my mind was almost fully occupied with the sensation in my feet and with those catastrophizing thoughts. Realizing this led to a vicious cycle of increased catastrophizing: ‘What an idiot – I ought to be able to focus on my work!’

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von Baeyer 2014

von Baeyer then realized his pain was caused by central sensitization due to repetition of identical physical stimuli (treadmill walking):

•allodynia (feeling a normal touch as painful)•windup (progressively stronger pain to the exact same stimulus)

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von Baeyer 2014

“With this insight, the cure was obvious: I had to vary the stimulus. When the sharp gravel sensation starts, I kick off my shoes and continue walking in my socks or bare feet; if I am already barefoot when the sensitization begins, I put my socks and shoes back on.”

changing catastrophizing can change central sensitization: pain 1/10, unpleasantness 3/10

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von Baeyer 2014

“Reduction in secondary hyperalgesia was associated with reduced pain catastrophizing, suggesting that changes in central sensitization are related to changes in pain-related cognitions. Thus, we demonstrate that central sensitization can be modified volitionally by altering pain-related thoughts.”

Salomons et al. 2014. PAIN.

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researcher-subjects?

1. the results were obtained through researchers introspecting personal pain

2. observations about specific pain experiences3. the observations have been integrated into

our knowledge of pain4. the observations have been replicated in

studies using standard experimental designs and methods

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bias and researcher-subjects

the participation of researcher-subjects may minimize and eliminate bias

preferable for formulating hypotheses and designing experiments than relying on published accounts or the imagination of others

multiple researcher-subjects likely optimal

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a first-person neuroscientific method of pain

“experiential-phenomenological method”

Price DD, Aydede, M (2006) Pain: New Essays on its Nature and the Methodology of its Study, M Aydede (Ed.), Cambridge, Mass: MIT Press.

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overview

experimental tasks phase

identify common factors within pain experiences horizontal (first-person)

‘phenomenal structure’identify common factor interrelationships

identify common factor-brain relationships

vertical (third-person)‘brain structure’

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horizontal phasehorizontal phase stages experimental subjects

1 question and observe

researcher-subjects2 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

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horizontal phase

1. 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

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horizontal phase

2. describing pain from the first-personverbal/written self-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’

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horizontal phase

3. 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’

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horizontal phase

‘Feel bothered by this and distressed’can reduce to‘I have a feeling of intrusion related to this pain’

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horizontal phase

definitional hypotheses: experiential factors commonly present during a pain

functional hypotheses: common factor interrelationships

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horizontal phase

sample definitional hypotheses:1. an intense burning throbbing sensation in

the hand 2. an experienced intrusion or threat associated

with this sensation3. a feeling of unpleasantness associated with

this felt intrusion or threat

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horizontal phase

sample 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

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horizontal phase

4. applying psychophysical methods

controlled observation of ratings of experiential factors (pain aversion) or sub-factors (concern)

rating scale methods (ratio scales)

subjects are not researchers

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vertical phase

correlate horizontal results with brain activity to establish possible causal relationships

patterns of brain activity that co-vary with different factors of pain could be identified

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Rainville et al. 1997

subjects 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 sensation1 ↑ pain unpleasantness no

change2 ↓ pain unpleasantness

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Rainville et al. 1997

↑ unpleasantness increased magnitudes of pain-unpleasantness ratings and neural activity in ACC

no change in ACC for ↓ unpleasantness

no change in S1 activity and magnitude ratings of pain sensation intensity in both conditions

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Rainville et al. 1997

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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 s

condition hypnotic suggestion unpleasantness1 ↑ sensation intensity

no change2 ↓ sensation intensity

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Hofbauer et al. 2001

↑ intensity increased magnitudes of pain-intensity ratings and neural activity in S1

no change in S1 for ↓ intensity

no change in ACC activity and magnitude ratings of pain unpleasantness in both conditions

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significance of pain-brain relations

changes in experience and brain activity cannot be predicted only by stimulus properties

the neural activity sufficient for a given pain quality of pain does not prove it exists within one brain region

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future issues

less well-known introspective methods should be used in the study of pain

relate pain and brain activity in real-time using neurofeedback techniques

promote first-person neuroscience of pain within pain associations (SIGs)

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acknowledgements

NSC 102-2811-H-038-001

Brain and Consciousness Research Centerhttp://consciousbrain.tmu.edu.tw/main.php