Roles of Synaptic Plasticity in Functional Recovery After Brain Injury

Abstract

Patients with brain injury or stroke suffer from sensory-motor disorder caused by the loss of function of damaged brain tissues. The goal of neurorehabilitation is to facilitate the recovery of the impaired sensory-motor function through new learning in the remaining intact brain tissues. Synaptic plasticity, i.e., long-term potentiation and depression of synaptic transmission, and new synapse formation through axonal sprouting, are assumed to underlie such new learning. To further elucidate the roles of synaptic plasticity in neurorehabilitation, four items are addressed in this chapter. First, the characteristics of synaptic plasticity in the intact hippocampus, cerebellum, and red nucleus are reviewed. Second, the spinal, cerebellar, and cerebral mechanisms underlying the recovery of grasping or gripping movement after unilateral spinal cord injury are discussed as an experimental model of neurorehabilitation of motor function. Third, the neural mechanisms underlying the recovery of somatosensory and vestibular functions are discussed as an experimental model of the neurorehabilitation of sensory function after injury of their pathways in the central or peripheral nervous system. Finally, recent progress in neurorehabilitation techniques, noninvasive transcranial brain stimulation, neuroprosthesis, and regenerative medicine, including the induced pluripotent stem cell technology, is reviewed in relation to synaptic plasticity.