Implications for brainstem recovery from studies in primates after sensory loss from arm

For decades,researchers have known that when neurons lose their activating inputs,they can atrophy and even die.For example,removing sensory nerve inputs from the arm to the spinal cord after amputation or cutting the spinal nerves can shrink the post-synaptic target zones(e.g.,Woods et al.,2000).From touch receptors for the hand and arm,primary nerve afferents enter the spinal cord,and axons travel in the dorsal columns to target the cuneate nucleus(Cu)of the brainstem on the same side of the body(Figure 1).When sensory loss is unilateral,the overwhelming result is for the associated primary target zone to shrink in total size(cross-sectional area),as compared to the size of the opposite side.

Anatomical changes in the somatosensory system after large sensory loss predict strategies to promote functional recovery after spinal cord injury

Among cases of spinal cord injury are injuries involving the dorsal column in the cervical spinal cord that interrupt the major cutaneous afferents from the hand to the cuneate nucleus（Cu）in the brainstem.Deprivation of touch and proprioceptive inputs consequently impair skilled hand use.