Thalamic projections to the posterior suprasylvian gyrus and the ventrally adjacent cortex in the cat traced with horseradish peroxidase.

The present study has been undertaken to elucidate the thalamic projections to the posterior suprasylvian gyrus (PSG) and the ventrally adjacent areas in the cat using retrograde axonal transport of horseradish peroxidase. The posterior part of the PSG, area 19 b, receives fibers mainly from the dorsolateral part of the medial pulvinar nucleus, and a lesser number from the lateral pulvinar nucleus. It receives a few fibers from the inferior pulvinar nucleus and the medial interlaminar nucleus (NIM) of the lateral geniculate. The anterior part of the PSG, area 21 b, receives a large number of fibers from the medial pulvinar nucleus, particularly its dorsolateral part, and less numerous fibers from the inferior pulvinar and lateral pulvinar nuclei. It receives only a few fibers from the lateral geniculate (NIM), suprageniculate and intralaminar nuclei, and in some cases from the ventral anterior and ventral lateral nuclei. Area 20 has thalamic connections similar to area 21 b, but it receives more fibers from the ventrolateral part of the medial pulvinar nucleus, nucleus, and receives less numerous fibers from the inferior pulvinar nucleus. It receives a few fibers from laminae C1-C2 and NIM of the lateral geniculate nucleus. Area 36 receives many fibers from the ventrolateral part of the medial pulvinar nucleus and the suprageniculate nucleus, a lesser number from the other parts of the medial pulvinar nucleus, and some fibers from the medial geniculate nucleus, particularly its dorsal principal part.