Cortical projection of canines to the primary somatic area of the dog

Experiments were performed on 25 male dogs kept under pentobarbital sodium anesthesia. The right hemisphere was widely exposed through craneotomy of the bone over the somatic area; dura removed and the cortex then exposed. Pressure stimuli were applied to the superior ipsi and contralateral canines with a suitable stimulator, intensity, pressure and duration were controlled by a programmed unit. The results show that there was a heavier projection from the contralateral canine as compared with the evoked activity by the ipsilateral one. Latencies were shorter for contralateral evoked potentials than for the ipsilateral; on average they were 18 msec for the contralateral projection against 21 msec for the ipsilateral evoked activity. Comparison of the cortical foci of projection of superior and inferior contra and ipsilateral canines suggested that their projection in SI had a somatotopic distribution: the inferior contralateral canine was located dorsally and caudally in regard to the superior contralateral canine and the projection of the inferior ipsilateral canine was medial and caudal in regard to the superior ipsilateral projection. Activity determined by either canine at the cortical level showed overlapping in projection areas as shown by the maps.