Neurophysiology of Nociception: Modulation

Question 1

What does modulation refer to?

Answer 1

the adjustments made by either the “bottom-up” control of neurons responsible for the transmission of the nerve impulse from the periphery to the cortex or to the top-down control of the higher brain regions

Question 2

What can modulation increase?

Answer 2

the nociceptive response of the perception of nociception–> hyperalgesia/ allodynia)

Question 3

What can modulation decrease?

Answer 3

the nociceptive response or perception of nociception –> Analgesia

Question 4

What can persistent pain may be the result of what?

Answer 4

an increase in nociceptive afferents and/or a decrease in inhibition and/or an increase in central excitation

Question 5

“Bottom Up” pain gating

Answer 5

transitory pain suppression via non-noxious peripheral sensory stimulation

Question 6

How long does the “Bottom Up” effect last?

Answer 6

only last as long as non-nociceptive stimulation

Question 7

Gate control theory was proposed by?

Answer 7

Neuroscientists R. Melzack and P. Wall in the 1960’s

Question 8

What is the Gate control theory?

Answer 8

It proposed that the spinal cord contained a neurological pain “gate”, which could be “shut” in order to prevent nociception

Question 9

Neural mechanisms of “Bottom Up” pain modulation as explained by Gate Control theory

Answer 9

• Non-noxious stimuli can activate peripheral mechanoreceptors
• Contralateral of these large non-noxious sensory fibers can facilitate inhibitory (GABA-ergic) interneurons which synapse on and inhibit WDR’s

Question 10

Activation of the inhibitory interneurons in the “Bottom up” pain modulation, results in what?

Answer 10

inhibition of nociceptive transmission from nociceptive fibers to WDR’s
- input from non-noxious stimuli can presynaptically “override” painful input

Question 11

What does it mean when a non-noxious stimuli can presynaptically “override” painful input?

Answer 11

Something like pressure can result in prevention of the nociceptive signal traveling to the CNS

Question 12

“Top Down” pain gating involves…

Answer 12

the exertion of conscious and unconscious cognitive control over the perception of pain and involves several mechanisms

Question 13

What are several mechanisms involved in the “Top Down” pain gate?

Answer 13

• Learned expectations that involve implicit/explicit learning & memory
• Conditioned emotional responses
• Emotional priming effects
• “Placebo” effects
• Shifts in attention

Question 14

What regions are included in the various locations of the cerebral cortex and other higher processing regions that send projections as part of the descending systems that modulate transmission of ascending pain signals?

Answer 14

• S-S cortex
• Hypothalamus
• Thalamus
• Amygdala
• Periaqueductal grey (PAG)
• Several brainstem nuclei

Question 15

Several brainstem nuclei involved in modulation of pain?

Answer 15

locus coeruleus (NE/NA), raphe nuclei (5-HT), and ventral tegmental area (VTA: DA)

Question 16

What does stimulation of the PAG in rodents result in?

Answer 16

elimination of pain perception

Question 17

Where do all of the descending regions that modulate transmission of pain send projections to?

Answer 17

to the dorsal horn of the spinal cord to influence WDR neurons
- directly or indirectly through the action of inhibitory interneurons (inhib/facilitate nociceptive signals)

Question 18

Overview flow chart on pg. 21

Answer 18

I’d look at it if i were you