Laterality effects in somesthesis following cerebral commissurotomy in man

Abstract A variety of basic somatosensory tests carried out on a patient with surgical section of the cerebral commissures revealed a marked separation of somesthetic effects from right and left extremities and from right and left sides of the trunk. Predominantly contralateral projection of somesthesis was evident; the presence of any ipsilateral representation at all four regions below the neck remained questionable. Bilateral projection was indicated in results from the face and the top and back of the head with equal representation on both sides. Comparatively little functional impairment was the rule when the sensory and motor output involved the same hemisphere, but severe impairment and complete incapacity were evident when right-left cross integration was required. These and similar results in the present case suggest that in the absence of cerebral damage during infancy, transcallosal interaction is of critical importance for utilization of ipsilateral somesthetic data particularly when the left extremities participate in activities involving the symbolic functions of the dominant hemisphere.