This study aims to investigate the thalamic afferents to the posterior suprasylvian gyros (PSG) and its ventral continuation in the cat using the method of retrograde axonal transport of horseradish peroxidase. The PSG is divided into areas 19a, 19b and 21b. Area 19a is included in area 19 of Otsuka and Hassler (1962), while area 19b is area 19 in PSG of Tusa et al. (1979), exclusive of area 19a. Area 19b receives many fibers from the dorsolateral part of the medial pulvinar nucleus, and less numerous fibers from the lateral and inferior pulvinar nuclei, but it receives only few fibers from the medial interlaminar nucleus (NIM) of the lateral geniculate nucleus. Area 21b, the anterior part of the PSG, receives numerous fibers from the medial pulvinar nucleus, particularly its dorsolateral part, and a lesser number from the lateral and inferior pulvinar nuclei. It receives very few fibers from the lateral geniculate (NIM), suprageniculate and intralaminar nuclei. The ventral continuation of the PSG comprises areas 20 and 36. Area 20 has thalamic connections similar to area 21b. However, it receives more fibers from the lateral pulvinar nucleus, and less fibers from the inferior pulvinar nucleus. It receives only a few fibers from both NIM and C1-C2 of the lateral geniculate nucleus and from the suprageniculate, dorsal lateral, posterior lateral and intralaminar nuclei. Area 36 receives projections largely from the ventrolateral part of the medial pulvinar nucleus and from the suprageniculate nucleus. It should be noted that area 36 receives some fibers from the medial geniculate nucleus, particularly its dorsal principal part.
Posterior suprasylvian gyrus