Spinal pathways projecting to the cerebral first somatosensory area in the monkey.

1. Potentials evoked with short latency in the cerebral post-central gyrus after intradermal electrical, or adequate light tactile stimulation of the contralateral body half have been studied in the monkey, before and after transection of different spinal pathways at the upper cervical level.2. Initially, positive potentials evoked by both types of stimulus were recorded after transection of the dorsal funiculi with the same somatotopic, topographical distribution as before the lesion.3. The potentials recorded after transection of the dorsal funiculi could be evoked via one pathway located in the dorsal half of the lateral funiculus ipsilateral to the afferent input, and another pathway located, at least partially, in the ventral funiculus contralateral to the afferent input.4. Of these two pathways, the crossed ventral pathway was found necessary to keep the topographical distribution of the evoked potentials unaltered.