Somatosensory System and Pain

Prof. Marshall Devor, Ph.D.Dept. of Cell & Animal Biology and Center for research on Pain Institute of Life SciencesHebrew University of Jerusalem

lecture 6: Ascending pathways

פיסיולוגיה מורחבפיסיולוגיה מורחב 08-908-9

primary sensory neurons

perception vs.perception vs.regulationregulation

Spinal white matterpathways

antero-lateralcolumn

dorsal column

dorsal column – medial lemniscussystem

hand

foot

AA LTM LTMafferentsafferents

dorsal column nuclei

thalamus (ventro-basal nucleus)VPL, VPM

somatosensorycortex (S1)

dorsal column –medial lemniscussystem

light touch and vibration sense

anterolateral column system(spino-bulbo-thalamic system)

all types of all types of afferentsafferents

hand

foot

thalamus (ventro-basal nucleus)VPL, VPM

somatosensorycortex (S1)

spino-bulbo-thalamic system

which sense ?

brainstemnuclei"bulbo-"

spino-bulbo-thalamic system

dorsal column – medial lemniscus systemlight touch and vibration

spino-bulbo-thalamicsystemwhich sense ??

tabes dorsalis

anterolateral column system(spino-bulbo-thalamic system)

all types of all types of afferentsafferents

hand

foot

dorsal column – medial lemniscus systemlight touch and vibration

spino-bulbo-thalamicsystemall somato-visceral senses

primary sensory neurons

““medial pain pathway”medial pain pathway”lamina I (nociceptive) parabrachial n. (pons)amygdala + hypothalamus

succinyl dehydrogenase

barrel field (van der Loos)

homunculus

functional magneticresonance imaging fMRI

saggital human brain

anterior cingulate gyrus

CCoghill et al. 2003

constant stimulus, variable sensory response among subjects

propriospinal system

propriospinaltract

Somatosensory System and Pain

Prof. Marshall Devor, Ph.D.Dept. of Cell & Animal Biology and Center for research on Pain Institute of Life SciencesHebrew University of Jerusalem

lecture 6: Ascending pathways

פיסיולוגיה מורחבפיסיולוגיה מורחב

primary sensory neurons

• heterogeneity of primary afferents (heterogeneity of primary afferents (labeled line theory)labeled line theory)• divergence + convergence divergence + convergence different heterogeneity of second different heterogeneity of second

order projection neuronsorder projection neurons (2x specific, WDR, multireceptive)(2x specific, WDR, multireceptive)

• dynamic (RF size & response properties, central sensitization )dynamic (RF size & response properties, central sensitization )• multiple ascending pathwaysmultiple ascending pathways• multiple terminal areasmultiple terminal areas• descending control (feedback, feedforward, anticipation)descending control (feedback, feedforward, anticipation)

AQ

P

AQ

P

for every unique stimulus, a unique constellation of neural population activity

"Population activity theoryPopulation activity theory"

“bottom-up” vs. “top-down”