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

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

  1. 1. First-Person Neuroscience of Pain: Puzzles, Methods and Data Simon Peter van Rysewyk Graduate Institute of Medical Humanities, Taipei Medical University Brain and Consciousness Research Center, Taipei Medical University-Shuang Ho Hospital
  2. 2. my focus today a puzzle about introspection and the limits of pain science researcher-subjects “experiential-phenomenological method” Simon van Rysewyk 2
  3. 3. 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 Simon van Rysewyk 3
  4. 4. 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 4Simon van Rysewyk
  5. 5. 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 5Simon van Rysewyk
  6. 6. 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 6Simon van Rysewyk
  7. 7. 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 7Simon van Rysewyk
  8. 8. 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 8Simon van Rysewyk
  9. 9. cartesian dualism PAIN begins in the PNS ascends in specific pathways ends in a specific brain center introspection of pain by the non-physical “soul” Simon van Rysewyk 9 Rene Descartes Treatise of man (1662)
  10. 10. 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 Simon van Rysewyk 10
  11. 11. 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 11Simon van Rysewyk
  12. 12. 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” 12Simon van Rysewyk
  13. 13. 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 13Simon van Rysewyk
  14. 14. 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? 14Simon van Rysewyk
  15. 15. 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 Simon van Rysewyk 15
  16. 16. 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 Simon van Rysewyk 16
  17. 17. 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 Simon van Rysewyk 17
  18. 18. 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 Simon van Rysewyk 18
  19. 19. 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 Simon van Rysewyk 19
  20. 20. two scientific uses of introspection non-researcher-subject report (verbal/written) researcher-subject report (verbal/written) double-pain catastrophizing and sensitization Simon van Rysewyk 20
  21. 21. 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) Simon van Rysewyk 21
  22. 22. double pain Simon van Rysewyk 22
  23. 23. 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 Simon van Rysewyk 23
  24. 24. 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 Simon van Rysewyk 24
  25. 25. 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 Simon van Rysewyk 25
  26. 26. 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.” Simon van Rysewyk 26
  27. 27. 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!’ Simon van Rysewyk 27
  28. 28. 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) Simon van Rysewyk 28
  29. 29. 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 Simon van Rysewyk 29
  30. 30. 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. Simon van Rysewyk 30
  31. 31. researcher-subjects? 1. the results were obtained through researchers introspecting personal 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 Simon van Rysewyk 31
  32. 32. 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 Simon van Rysewyk 32
  33. 33. 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. Simon van Rysewyk 33
  34. 34. overview Simon van Rysewyk 34 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’
  35. 35. horizontal phase Simon van Rysewyk 35 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
  36. 36. 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 Simon van Rysewyk 36
  37. 37. horizontal phase 2. describing pain from the first-person verbal/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’ Simon van Rysewyk 37
  38. 38. 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’ Simon van Rysewyk 38
  39. 39. horizontal phase ‘Feel bothered by this and distressed’ can reduce to ‘I have a feeling of intrusion related to this pain’ Simon van Rysewyk 39
  40. 40. horizontal phase definitional hypotheses: experiential factors commonly present during a pain functional hypotheses: common factor interrelationships Simon van Rysewyk 40
  41. 41. horizontal phase sample 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 Simon van Rysewyk 41
  42. 42. 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 Simon van Rysewyk 42
  43. 43. 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 Simon van Rysewyk 43
  44. 44. 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 Simon van Rysewyk 44
  45. 45. 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 Simon van Rysewyk 45 condition hypnotic suggestion sensation 1 ↑ pain unpleasantness no change2 ↓ pain unpleasantness
  46. 46. 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 Simon van Rysewyk 46
  47. 47. Rainville et al. 1997 Simon van Rysewyk 47
  48. 48. Hofbauer et al. 2001 Simon van Rysewyk 48 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 unpleasantness 1 ↑ sensation intensity no change 2 ↓ sensation intensity
  49. 49. 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 Simon van Rysewyk 49
  50. 50. 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 Simon van Rysewyk 50
  51. 51. 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) Simon van Rysewyk 51
  52. 52. acknowledgements Simon van Rysewyk 52 NSC 102-2811-H-038-001 Brain and Consciousness Research Center