COGNITIVE AND SENSORIMOTOR FUNCTIONING IN THE ABSENCE OF THE CORPUS-CALLOSUM - NEUROPSYCHOLOGICAL STUDIES IN CALLOSAL AGENESIS AND CALLOSOTOMIZED PATIENTS

The aim of the present study was to investigate the role of the corpus callosum in cognitive and sensori-motor functioning as measured by a neuropsychological test battery. After a brief review and analysis of the literature, we report our own studies in acallosal subjects (n = 9 ) and callosotomized patients (n = 25). The main instrument of evaluat ion was the Michigan Neuropsychological Test Battery. This battery was supplemented by age-appropriate intelligence tests. The performance o f the acallosal group was compared to that of two matched control grou ps: one group consisting of children and adolescents that attended the same school as the acallosals and a second group of subjects recruite d from regular schools. The callosotomized patients, tested pre- and p ost-operatively, served as their own controls. Taken together, the res ults of the reviewed and personal studies suggest that absence of the corpus callosum does not necessarily impede cognitive functioning. How ever, samples drawn from clinical populations tend to show a larger va riability as to their mental abilities. In keeping with previous findi ngs, our results indicate that the corpus callosum does play a role in bimanual motor coordination although other pathways (probably ipsilat eral and/or subcortical) may provide adequate compensation in many cas es. The data further suggest that the corpus callosum may be important for interhemispheric transfer of tactuo-motor learning when a spatial component is involved. Finally, our results are consistent with a fac ilitatory role of the corpus callosum in cognitive and sensori-motor f unctioning which allows for interhemispheric compensation as part of c erebral reorganization in the case of unilateral brain damage.