Growth of new brainstem connections in adult monkeys with massive sensory loss

When adult monkeys lose feeling in their arm, the part of the brain that used to handle those sensations can start responding to the face instead. This study shows that after such sensory loss, nerve fibers from the face area of the brainstem actually grow into the area that used to receive signals from the arm. This new growth of nerve connections may explain why the face takes over the brain area that was previously used by the hand.

• 1
  After dorsal column lesions or arm amputation, face afferents from the trigeminal nucleus sprout and grow into the cuneate nucleus in adult monkeys.
• 2
  Cortical reorganization occurs, with the deprived hand cortex becoming responsive to inputs from the chin.
• 3
  The extent of neuronal growth varied among animals, with the largest extent observed in a macaque monkey with limb amputation and in the owl monkey with a dorsal column lesion.