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Cortical Reorganization in Somatosensory Cortex: A Biological Approach to Lost Sensory Nodes. Dan Stiehl wdstiehl@mit.edu MAS.965. Somatosensory Maps. Each Region of Area 3b and Area 1 maps to a different body location Owl Monkey shown. Principles of Neuroscience 4 th Edition, Chapter 20.

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cortical reorganization in somatosensory cortex a biological approach to lost sensory nodes

Cortical Reorganization in Somatosensory Cortex:A Biological Approach to Lost Sensory Nodes

Dan Stiehl

wdstiehl@mit.edu

MAS.965

somatosensory maps
Somatosensory Maps
  • Each Region of Area 3b and Area 1 maps to a different body location
  • Owl Monkey shown

Principles of Neuroscience 4th Edition, Chapter 20

wiring of the sensor network
“Wiring” of the Sensor Network
  • Originally believed that all the cortical maps of the body’s surface were hard wired from birth
  • Recent work has shown that in fact cortical maps are very plastic and can rewire themselves based on changes in the body
  • Details of the topographic map vary from animal to animal thus implying differences in wiring
when one node dominates neighbors
When One Node Dominates Neighbors
  • Monkeys trained to touch disk with fingertips for several months
  • Finger tip regions expanded into proximal phalanges region
  • Use of fingertips strengthened connections

Principles of Neuroscience 4th Edition, Chapter 20

when nodes combine cells that fire together wire together
When Nodes Combine: “Cells that Fire Together, Wire Together”
  • Surgically connected tissue of two monkey fingers
    • Connected fingers are always used together
  • Sharp discontinuity between fingers was not seen in cortex

Principles of Neuroscience 4th Edition, Chapter 20

syndactyly in humans
Syndactyly in Humans
  • Fusion of fingers together from birth
    • Size of the representation of the hand is less than in normal humans
    • No separation of fingers
  • Surgically separating fingers
    • Within weeks they show individual representations of fingertips
    • Hand representation expands to almost normal size (3-9 mm)

Principles of Neuroscience 4th Edition, Chapter 20

when a node is removed
When a Node is Removed
  • Study of deafferented monkeys
    • The sensory nerves to the arm were severed at the upper limb
    • After 10 years or more, the cortical representation for the face had expanded into the cortex area for the hand
    • Stimulation of the face of these monkeys evoked responses in the area that normally represented the hand
when a node is removed8
When a Node is Removed
  • Phantom Limbs
    • Possibly due to the rearrangement of cortical circuits
    • Remapping of referred sensations
    • Just like in the monkeys, the face and upper arm regions occupy the territory previously devoted to the hand

Principles of Neuroscience 4th Edition, Chapter 20