Lecture 25 Flashcards
What is pain?
a multimodal phenomenon containing a sensory component and an
affective or emotional component
What is inflammatory pain?
caused by damage to tissues and joints or by tumour
cells
What is neuropathic pain?
caused by damage to the central nervous system
* e.g. carpal tunnel syndrome, spinal cord injuries, etc.
What is nociceptive pain?
caused by
activation of nociceptors in the skin,
which signal impending damage
Describe the direct pathway model of pain
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.
Describe gate control model
gate control model still
assumes that pain signals enter the spinal cord from the
body and are transmitted to brain
Describe the network involved in pain perception
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)
Describe mechanoreceptors and the gate control model
receptors carrying information
about non-painful tactile-based stimuli
mechanoreceptors send inhibitory signals (-) to
transmission cells, closing the gate
Describe nociceptors and gate control model
receptors carrying information about
painful tactile-based stimuli
nociceptors send excitatory signals (+) to
transmission cells, opening the gate
Describe central control and gate control model
receive signals related to cognitive
function (attention, expectations distractions, etc.)
this module also sends inhibitory signals (-) to
transmission cells, closing the gate
Describe video game study
- 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)
Describe the Bingel study
- 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)
Describe Bingel results
- 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
Describe the nocebo effect
negative placebo effect
the increase in
pain accompanying the
negative expectation
Describe top down processes and emotions
- 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)
What subcortical brain areas are involved in pain perception?
Subcortical areas, including the
hypothalamus, amygdala, and the
thalamus
what cortical areas are involved in pain perception?
S1, the insula,
and the anterior cingulate (ACC) and
prefrontal cortices (PFC)
What are the cortical and subcortical areas involved in pain perception called?
The pain matrix
Describe Hofbauer study
- 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
What are endorphins?
Brain tissue releases neurotransmitters called
endorphins, which bind to same receptors as
opiates
Describe naloxone and endorphins
- 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
Describe the capsaicin study
- 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)
Describe ACC
- 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
Describe Eisenberger study
- 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)
