Somatosensory receptive fields of fibres in the rostral corpus callosum of the cat.

The corpus callosum is the principal neocortical commissure which transmits lateralized information between the hemispheres. The aim of the present experiment was to study the receptive field (RF) properties of somatosensory callosal fibres in the cat. The callosum was approached under direct visual control and axonic responses were recorded under N2O anaesthesia using tungsten microelectrodes or, mostly, glass micropipettes. RFs representing all the sensory submodalities tested (light touch, medium and deep pressure, joint movement and light pinches) were found to be present in the axons which travelled through the callosum. Rapidly adapting units were more common than slowly adapting ones. The axial and para-axial portions of the body accounted for about three-fifths of all RFs, followed by the head (about one-fifth), with the rest responding to stimulation of the extremities. The medial borders of most of the unilateral RFs situated on the trunk and, to a lesser degree, the head, extended to the mid-line. The results are interpreted in terms of the roles of the corpus callosum in mid-line fusion and interhemispheric transfer.