Plasticity in the Motor Network Following Primary Motor Cortex Lesion

Abstract

The behavioral deficits following stroke are particularly evident in the fine control of force, movement, and posture of the arm and hand. However, functional recovery continues in the weeks and months after the initial lesion. Various animal models of stroke have been used to investigate the mechanisms involved with this recovery. These studies have revealed a dramatic physiological and structural reorganization not only within the tissue surrounding the lesion but also in other distant areas of the brain in both the contralesional and ipsilesional hemispheres. These latter changes suggest that functional recovery could be dependent upon the adaptive plasticity of intact, remaining brain structures, a phenomenon often referred to as “vicariation of function”. In the case of a lesion in the primary motor cortex (M1), the premotor areas are particularly well positioned to substitute for the lost M1 function because of their extensive interconnections with other motor areas, their corticospinal outputs, and the movement-related activity they carry prior to the lesion. In the present chapter, the basic principles of organization of the primary motor and premotor cortex are reviewed with the addition of a few key studies carried out in monkeys that have contributed to our understandings of adaptive plasticity in the ipsilesional hemisphere after stroke.