HEMISPATIAL AND DIRECTIONAL PERFORMANCE BIASES IN MOTOR NEGLECT

Motivationally responsive motor deficits may occur in isolation or as part of more general neglect syndromes. We describe three patients wit h two discrete syndromes of isolated motor neglect, differentiated pri marily by their performance in motor tasks enacted within or toward th e contralesional hemispace, The lesions in our patients likely disrupt ed attentional interactions with two separable sensorimotor processing subsystems. Physiologic data support the existence of a parietal-late ral premotor circuit that processes information encoded in spatial coo rdinates referenced to the extrapersonal environment and of a basal ga nglionic-mesial premotor circuit that processes information mostly enc oded in egocentric skeletomotor coordinates. The correlation of ischem ic lesions resulting in hemispatial and directional biases in motor ne glect with disruption of known physiologic subsystems may provide the basis for rational cognitive rehabilitation of these higher-order moto r deficits. These observations are supported by recent PET studies tha t document the presence of specific attentional-motoric interactions w ithin discrete processing components of a distributed sensorimotor att entional network.