Problem 1
Chapter 7 – representation of pain in the brain (Apkarian et al.)
Defining a pain network in the brain
- regions associated with pain include:
o S1, S2, anterior cingulate cortex (ACC), insular cortex (IC), prefrontal cortex
(PFC), thalamus, cerebellum
- regions activated by pain receive either direct or indirect nociceptive input
o S1 and S2: input from somatosensory thalamus
o cingulate cortex: input from medial thalamic nuclei and lateral thalamic
regions
o IC: thalamocortical nociceptive input
- the most common subcortical pain-related activation takes place in the thalamus and
cerebellum
- nuclei in the thalamus receives nociceptive input from the dorsal horn, and the
cerebellum has reciprocal spinal connectivity
- PAG, nucleus accumbens and amygdala also observed active in pain studies
Brain processing the multidimensionality of pain
- somatosensory cortices important for sensory features (location, duration)
o S1 and S2 neurons code spatial, temporal and intensive aspects
- limbic and paralimbic regions (ACC and IC) important for emotional and
motivational aspect
- different studies show:
o ACC affective aspect of pain
o IC pain affect, pain perception: encodes subjective magnitude of pain
o PFC related to cognitive aspects of pain perception rather than pain affect
o Cerebellum modulation of visceral and somatic nociceptive responses
How do we distinguish location and quality of pain?
- differentiating types of pain:
o S1 cortex identifies locus of pain affecting the skin (cutaneous)
o IC also participates in localization
o IC reactions can be divided to nociceptive and pain-perceptive regions
- laterality of pain representation:
o bilateral activity in S2 and IC
o contralateral activity in S1
- temporal sequence:
o dual pain sensation elicited by a single stimulus is caused by different
conduction times in nociceptive A and C fibers, this is reflected in 2 sequential
brain activations
o first pain (S1) signals threat and provides sensory info for withdrawal, second
pain (ACC) attracts longer lasting attention and motivates behavioral
responses, both pains activate S2
o there’s a well-organized temporal sequence of brain activity that transforms
noxious stimulus to pain perception
, Brain’s role in modulating pain
- opiates in the brain:
o μ- opioid receptors are involved in regulation of the experience of pain,
including areas in descending inhibition (PAG, thalamus, amygdala) and areas
involved in complex and integrative aspects of pain (ventral BG, IC, ACC, PFC)
o capacity to activate neurotransmitters in response to sustained pain is a
function of the catechol O-methyltransferase (COMT) enzyme
- dopamine and pain:
o dopamine plays a role in pain modulation
o healthy individuals release dopamine in the striatum in response to pain
Chapter 7 – representation of pain in the brain (Apkarian et al.)
Defining a pain network in the brain
- regions associated with pain include:
o S1, S2, anterior cingulate cortex (ACC), insular cortex (IC), prefrontal cortex
(PFC), thalamus, cerebellum
- regions activated by pain receive either direct or indirect nociceptive input
o S1 and S2: input from somatosensory thalamus
o cingulate cortex: input from medial thalamic nuclei and lateral thalamic
regions
o IC: thalamocortical nociceptive input
- the most common subcortical pain-related activation takes place in the thalamus and
cerebellum
- nuclei in the thalamus receives nociceptive input from the dorsal horn, and the
cerebellum has reciprocal spinal connectivity
- PAG, nucleus accumbens and amygdala also observed active in pain studies
Brain processing the multidimensionality of pain
- somatosensory cortices important for sensory features (location, duration)
o S1 and S2 neurons code spatial, temporal and intensive aspects
- limbic and paralimbic regions (ACC and IC) important for emotional and
motivational aspect
- different studies show:
o ACC affective aspect of pain
o IC pain affect, pain perception: encodes subjective magnitude of pain
o PFC related to cognitive aspects of pain perception rather than pain affect
o Cerebellum modulation of visceral and somatic nociceptive responses
How do we distinguish location and quality of pain?
- differentiating types of pain:
o S1 cortex identifies locus of pain affecting the skin (cutaneous)
o IC also participates in localization
o IC reactions can be divided to nociceptive and pain-perceptive regions
- laterality of pain representation:
o bilateral activity in S2 and IC
o contralateral activity in S1
- temporal sequence:
o dual pain sensation elicited by a single stimulus is caused by different
conduction times in nociceptive A and C fibers, this is reflected in 2 sequential
brain activations
o first pain (S1) signals threat and provides sensory info for withdrawal, second
pain (ACC) attracts longer lasting attention and motivates behavioral
responses, both pains activate S2
o there’s a well-organized temporal sequence of brain activity that transforms
noxious stimulus to pain perception
, Brain’s role in modulating pain
- opiates in the brain:
o μ- opioid receptors are involved in regulation of the experience of pain,
including areas in descending inhibition (PAG, thalamus, amygdala) and areas
involved in complex and integrative aspects of pain (ventral BG, IC, ACC, PFC)
o capacity to activate neurotransmitters in response to sustained pain is a
function of the catechol O-methyltransferase (COMT) enzyme
- dopamine and pain:
o dopamine plays a role in pain modulation
o healthy individuals release dopamine in the striatum in response to pain
