Effects of cryogenic blocking of pulvinar upon visually evoked responses in the cortex of the cat

Abstract

Visually evoked responses on the suprasylvian and marginal gyri were markedly diminished in amplitude by cooling of the pulvinar. Both the early and late components of the evoked response on the suprasylvian gyrus were affected but only the afterdischarge or late components on the marginal gyrus were reduced. The latter effect was shown to be mediated by the suprasylvian gyrus. Cooling of the B layer of the lateral geniculate, which we have previously shown to be a source of visual input to the pulvinar, reduced both the early and late components of the responses on the suprasylvian and marginal gyri, whereas cooling of the A layer caused a reduction of only the primary response components on the marginal gyrus. These results are interpreted as demonstrating two visual input systems to the cortex, one via direct geniculostriate pathways and another from the B layer of the lateral geniculate via the pulvinar to the suprasylvian gyrus. The former is mainly responsible for the primary response components of the marginal gyrus and the latter for the afterdischarge or late components.