Can simultaneous bilateral movement involve the undamaged hemisphere in reconstruction of neural networks damaged by stroke?

Normalization of upper limb movement remains a difficult problem for a sign ificant subpopulation of hemiplegic stroke patients. Clinical observations prompted investigation of a novel approach using simultaneous identical bil ateral movements performed independently. We briefly report 12 controlled s ingle-case experiments using multiple-baseline designs across three separat e grasp/reach activities. Unilateral performance tests with the hemiplegic arm using the bilaterally trained actions demonstrated clinically and stati stically significant improvements in movement patterns. These improvements were specific to the trained movement and well maintained. Using recent lit erature we develop a theoretical model proposing that bilateral simultaneou s movement promotes interhemispheric disinhibition likely to allow reorgani zation by sharing of normal movement commands from the undamaged hemisphere . Disinhibition may also encourage recruitment of undamaged neurones to con struct new task-relevant neural networks. The potential contribution of spa red ipsilateral pathways in the damaged hemisphere, indirect corticospinal pathways and ipsilateral pathways from the undamaged hemisphere is discusse d.