Lecture 25 - Body Maps and Plasticity Flashcards
The pain caused by excessive cold is most accurately
described as ___________ pain.
nociceptive
you have a specific nociceptive receptor that is activated by specific pain: extreme cold, extreme heat, etc…
direct pathway model
very straight forward
you have nociceptors that are stimulated and once they get that signal it’s sent eventually to somatosensory cortex
the cortex elicits a withdrawl response: you pull your hand away
gate control model
the gate is holding in the pain
when the gate closes it turns off the transmission cell and if that cell isn’t active the pain can’t be felt
• Simple version proposed by
Melzack & Wall (1965).
• The “gate” consists of
substantia gelatinosa cells in
the spinal cord (SG- closes the gate and SG+ opens the gate).
• Input into the gate comes from: – Large diameter (L) fibers - information from tactile stimuli (mechanoreceptors). – Small diameter (S) fibers - information from nociceptors. – Central control - information from cognitive factors (from the cortex).
Input into the gate comes from:
– Large diameter (L) fibers -
information from tactile stimuli
(mechanoreceptors).
– Small diameter (S) fibers -
information from nociceptors: want to open the gate!
– Central control - information
from cognitive factors (from the
cortex): where attention or your mood comes into play: it can come down and try and close the gate
gate output …
…. is transmission cell (Tcell)
activity. More T-cell activity
means more intense pain.
− Pain decreases when the gate is closed by stimulation of SG- by
central control or L-fibers.
− Pain increases when stimulation of the S-fibers activates SG+ to open the gate.
− By this model, we can regulate
amount of pain sensed through
other tactile input (rub or scratch) or cognitive factors (mood or
attention).
perception of pain decreases
when gate is closed by stimulation of SG- by
central control or L-fibers.
perception of pain increases when
stimulation of the S-fibers activates SG+ to open the gate.
Central Control
Expectation
- when you are anticipating something is going to hurt, they experience more pain and vice versa
- EX: when surgical patients
are told what to expect, they request less pain medication and leave the hospital earlier. (hypnosis)
– EX: Placebos can also be effective in reducing pain.
Central Control
Shifting Attention
if you don’t look at it, it won’t hurt as much
in burn units: virtual reality technology has been used to keep patients’ attention on other stimuli rather than the pain-inducing stimulation: playing a game so they can shift their attention away from their body and helps to lessen the perception of pain
Central Control
Content of emotional distraction
participants could keep their hands in cold water longer when pictures they were shown were positive: when they saw positive pictures they could keep their hands in the water for longer and when the pictures were negative they kept their hands in the water for less time
your mood (affected by these pictures) can control how much pain you feel
According to the gate control model of pain perception, input to
the “gate” of the substantia gelatinosa (SG) comes in from large diameter (L) fibers, small diameter (S) fibers, and ‘central
control’ areas in the cortex. Which of these inputs is most
responsible for carrying nociceptive signals to open the gate?
S-fibers
How does the brain represent pain?
the pain matrix
- Subcortical areas include the hypothalamus, amygdala, and the thalamus: activated when someone reports they’re experiencing pain
- Cortical areas include S1 and S2 in the somatosensory cortex, the insula, and the anterior cingulate and prefrontal cortices.
- These areas taken together are called the pain matrix: many cortical and subcortical regions
can’t say that there is one region that is the pain region
How can we separate the sensory and affective (emotional)
components of pain?
Experiment by Hofbauer et al. (2001)
– Participants were presented with potentially painful stimuli and asked:
• Asked To rate subjective pain intensity (sensory): on a scale of 1-100 how much does that hurt
• To rate the unpleasantness of the pain (affective element): rate 1-100 of how much you don't like it
– Brain activity (PET scan) was measured while they placed their hands into unpleasantly hot water.
– Hypnosis - suggestions - (to modulate central control) was used to attempt to increase or decrease the sensory and affective components: how intense or unpleasant it was
• Results showed that: Hypnosis had major affect!
– Suggestions to change the
subjective intensity led to:
when they were told the water is very very hot they rated the intensity AND UNPLEASANTNESS higher
• Changes in perceived intensity
• Changes in unpleasantness
• Associated with changes in S1
activation.
– Suggestions to change the
unpleasantness of pain:
- Lowered ratings of unpleasantness.
- Did not affect perceived intensity: Hypnotic suggestion to change unpleasantness didn’t affect intensity: these two things can be pulled apart
• Activation in the anterior cingulate cortex (but not S1):
!! the intensity judgment seems to driven by what’s happening in somatosensory cortex which further drives what’s happening in unpleasant rating, but it doesn’t go the other way
Intensity Vs. Unpleasantness
if you manipulate intensity it is associated with changes in S1
if you change the perceived intensity you change the perception of unpleasantness
BUT if you change the perception of unpleasantness there is activation in anterior cingulate cortex BUT NOT in S1, which means the perception of intensity DOES NOT CHANGE
dissociable: this suggests that these two elements can be separate
S1 –> ACC
but NOT ACC –> S1
Suggestions to change the
subjective intensity led to:
• Changes in perceived intensity
• Changes in unpleasantness
• Associated with changes in S1
activation.
