ABSTRACT
The presence of ipsilateral motor control of axial and of proximal limb movements has been demonstrated in both animals and man. In animals investigations of visuo-motor performance following induced lesions of optic chiasma and corpus callosum highlighted the mechanisms of this control (Brinkman & Kuypers, 1972, 1973; Downer, 1959; Gazzaniga, 1969; Paillard & Beaubaton, 1974). The work of Kuypers (1964) and Lawrence and Kuypers (1968a, 1968b) on the organization of corticospinal pathways has permitted to address the problem of its anatomical basis. In man, the study of motor disturbances subsequent to division of the cerebral commissures (Gazzaniga, Bogen, & Sperry, 1967) and the analysis of apraxic deficits secondary to focal brain lesions (Geschwind, 1975) has allowed to suggest the existence of such an ipsilateral motor control. Human split-brain studies run into the difficulty of sending visual information to a single hemisphere for a sufficiently long lapse of time, hence the impossibility of thoroughly studying visuomotor performances. The presence of lateral homonymous hemianopia associated with a full callosal disconnection syndrome offers from this viewpoint a unique model which allows the investigator to study, unrestrained, the motor capacities of the only sighted hemisphere.
