The Development of Interhemispheric Transfer of Tactile Information in Cases of Callosal Agenesis

Abstract

Congenital absence of corpus callosum in relatively asymptomatic individuals raises the question of mechanisms responsible for interhemispheric transfer of information. Possible alternative methods of communication between the cerebral hemispheres involve the anterior commissure, subcortical commissural pathways, bilateral representation of functions that are normally predominantly under unilateral control, enhanced transmission of information on the ipsilateral sensory and motor pathways, and behavioral cross-cueing (Jeeves, 1990). Before it is possible to pinpoint a particular mechanism, it is necessary to determine whether subjects with congenital absence of the corpus callosum (ACC) differ from normal individuals when performing tasks that require interhemispheric transfer, and whether transfer deficits, where present, are similar in magnitude to those shown by patients with surgical section (partial or complete) of the corpus callosum. We report a study of seven cases of callosal agenesis using a tactile finger localization task previously shown to be sensitive to extent and location of acquired lesions of the corpus callosum (Geffen et al., 1985). Developmental improvements in interhemispheric transfer in normal children were also elicited using this task (Quinn and Geffen, 1986). However, the proposal that this improvement reflects the concomitant myelination of the corpus callosum between ages 5–11 years has been questioned (Pipe, 1991).