Lecture 25

Question 1

What is pain?

Answer 1

a multimodal phenomenon containing a sensory component and an
affective or emotional component

Question 2

What is inflammatory pain?

Answer 2

caused by damage to tissues and joints or by tumour
cells

Question 3

What is neuropathic pain?

Answer 3

caused by damage to the central nervous system
* e.g. carpal tunnel syndrome, spinal cord injuries, etc.

Question 4

What is nociceptive pain?

Answer 4

caused by
activation of nociceptors in the skin,
which signal impending damage

Question 5

Describe the direct pathway model of pain

Answer 5

an early theory that assumed pain is simply the
result of nociceptors being stimulated and sending signals to the brain
* One kind of problem with the direct pathway model was various kinds of evidence for
many kinds of exceptions:
* Pain can be affected by a person’s mental state
* Pain can occur when there is no stimulation of the skin
* Pain can be affected by a person’s attention
* Phantom limbs
* etc.

Question 6

Describe gate control model

Answer 6

gate control model still
assumes that pain signals enter the spinal cord from the
body and are transmitted to brain

Question 7

Describe the network involved in pain perception

Answer 7

This network involves three types of signals processed in
the dorsal horn of the spinal cord, whose integrated
output is sent to what are referred to as transmission cells
(whose activity is directly related to our perception of pain)

Question 8

Describe mechanoreceptors and the gate control model

Answer 8

receptors carrying information
about non-painful tactile-based stimuli
mechanoreceptors send inhibitory signals (-) to
transmission cells, closing the gate

Question 9

Describe nociceptors and gate control model

Answer 9

receptors carrying information about
painful tactile-based stimuli
nociceptors send excitatory signals (+) to
transmission cells, opening the gate

Question 10

Describe central control and gate control model

Answer 10

receive signals related to cognitive
function (attention, expectations distractions, etc.)
this module also sends inhibitory signals (-) to
transmission cells, closing the gate

Question 11

Describe video game study

Answer 11

• Virtual reality technology has been used to keep patients’ attention on other
  stimuli than the pain-inducing stimulation
• When surgical patients are told what to expect, they request less pain
  medication and leave the hospital earlier (Egbert et al., 1964)
• Another example of expectations mediating pain can be seen with placebos,
  which can be very effective at reducing pain (Finniss & Benedetti, 2005)

Question 12

Describe the Bingel study

Answer 12

• Bingel et al. (2011) systematically varied expectations for pain
• The researchers then reapplied the same stimuli and asked participants to
  again rate how painful they found it to be after manipulating expectations in
  one of four conditions: 1. baseline, 2. no expectation, 3. positive
  expectation, 4. negative expectation
  (conditions described in more detail on next slide)

Question 13

Describe Bingel results

Answer 13

• Baseline: No painkiller given, just saline solution
• No expectation: Saline solution switched to a painkiller (but participants were
  not told about the switch)
• Positive expectation: Saline solution switched to a painkiller (which participants were told about)
• Negative expectation: Saline solution switched to a painkiller (but participants were not told about), with warnings that their pain level may
  increase

Question 14

Describe the nocebo effect

Answer 14

negative placebo effect

the increase in
pain accompanying the
negative expectation

Question 15

Describe top down processes and emotions

Answer 15

• Another kind of top-down effect on pain perception relates to emotions
• deWied and Verbaten (2001): Participants kept their hands in cold water
  (~20C) for longer when they were shown positive pictures
• Roy et al. (2008): Participants rated cold water as less intense and less
  unpleasant while listening to pleasant music
• These two kinds of ratings can be
  thought of as tapping into distinct
  dimensions of pain (i.e. sensory and
  affective)

Question 16

What subcortical brain areas are involved in pain perception?

Answer 16

Subcortical areas, including the
hypothalamus, amygdala, and the
thalamus

Question 17

what cortical areas are involved in pain perception?

Answer 17

S1, the insula,
and the anterior cingulate (ACC) and
prefrontal cortices (PFC)

Question 18

What are the cortical and subcortical areas involved in pain perception called?

Answer 18

The pain matrix

Question 19

Describe Hofbauer study

Answer 19

• Hofbauer et al. (2001) asked
  participants to put their hands in cold
  water and rate both the subjective
  pain intensity, as well as the
  unpleasantness of the pain
• Hypnosis was used to try to increase or decrease either the sensory
  (intensity) or affective (unpleasantness) components of pain
• Suggestions to change the intensity were associated with changes in S1
• Suggestions to change the unpleasantness were associated with changes in ACC

Question 20

What are endorphins?

Answer 20

Brain tissue releases neurotransmitters called
endorphins, which bind to same receptors as
opiates

Question 21

Describe naloxone and endorphins

Answer 21

• Endorphins reduce pain
• Injecting naloxone blocks the receptor sites,
  causing more pain
• Naloxone also decreases the effectiveness of
  placebos (implicating endorphins in top-down
  effects!)
• People whose brains release more endorphins
  can withstand higher pain levels

Question 22

Describe the capsaicin study

Answer 22

• Benedetti (1999) injected capsaicin (active component of chilli peppers that causes
  a burning sensation) just under the skin in four places: left/right hand, left/right foot
• Also applied a placebo cream (which
  participants were told had analgesic properties)
  on one or two of these locations, then took
  subjective ratings of pain
• Results suggest effects of placebos are
  localized (e.g. if you expect just your hand to
  feel less pain, that will be what you perceive
  and your feet will not ‘benefit’ from the placebo)

Question 23

Describe ACC

Answer 23

• Klimecki et al. (2014) showed that participants assigned to an empathy
  training condition had greater ACC activation in response to seeing videos of
  other people getting hurt

Question 24

Describe Eisenberger study

Answer 24

• Eisenberger et al. (2015) asked whether rejection actually
  ‘hurts’ using an experiment involving a video game that
  essentially consisted of a virtual game of keep away
• A ball was passed around between two players but the
  third (who was always the experimental participant) was
  never passed to
• Dorsal anterior cingulate cortex (dACC) was found to
  be activated, in step with degree of subjective feelings
  of reported social distress (i.e. how badly they felt on
  account of feeling left out)

Question 25

Describe physical-social pain overlap hypothesis

Answer 25

overlapping regions of the brain are associated with both physical and socially-based pain