Michel Poncet Daniel Beaubaton André Ali-Chérif
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.
Liliane S. was left-handed, left-footed, and left-eyed. Her parents and siblings were right-handed. At the age of 14 ½ she underwent surgery for a hematoma occupying the anterior portion of the corpus callosum. The rostral half of the corpus callosum was sectioned and the hematoma removed. A second and third