Intermanual information transfer in patients with lesions in the trunk of the corpus callosum.

Interhemispheric transfer of haptic information was examined in six partially callosotomized patients and three control subjects. Three different portions of the trunk were severed in different subjects. The most anterior 10 mm of the trunk, anterior to the foramen of Monro, was sectioned in one patient. Three other patients had lesions restricted to the anterior part of the trunk posterior to the foramen of Monro. The posterior third of the trunk was damaged in two patients. The splenium, genu and rostrum of the corpus callosum were intact in all six patients, as were the anterior and hippocampal commissures. Poor transfer of haptic information was found only in the three patients with the lesion located in the anterior part of the trunk posterior to the foramen of Monro. The functional anatomy of this region is discussed. It is assumed to house fibers responsible for interhemispheric transfer of complex tactile information.