Projections to the Cerebral Cortex from Afferents of the Interosseous Nerves of the Cat

Evoked focal potentials from the contralateral fore‐ and hindlimb interosseous nerves Int.f. and Int.h. as well as from Pacinian afferents were recorded in sensorimotor cortex and in S II in cats anaesthetized with chloralose. Low threshold, short latency potentials from Int.f. were evoked in the lateral sigmoid gyrus, in the region of the post cruciate dimple, in the rostral bank of the lateral ansate sulcus, in the lower bank of the anterior suprasylvian sulcus and in S II. The shortest latencies varied between 5.0–6.0 msec. Mechanical stimulation of dissected clusters of Pacinian receptors in the interosseous region evoked cortical responses in the same areas with slightly longer latencies. Low threshold electrical stimulation of Int.h. afferents evoked in addition to the known projection to S II (McIntyre 1962) initially positive potentials in two loci of the postsigmoid gyrus, one on the dorsal, the other on the medial aspect of the hemisphere. The latencies in these loci were as short as those in S II. i.e. 9.5–10.0 msec. Zonal convergence between projections from interosseous and Group I muscle afferents was observed. The Int.f. path ascends in the dorsal column. A cortical potential was however, evoked in the postsigmoid gyrus by electrical stimulation of high threshold Int.h. afferents after transection of the dorsal columns at cervical level.