Marginal and extramarginal cortical lesions and visual discrimination by cats.

75 mongrel cats learned a shape discrimination with 0, 1, or 2 irrelevant cues. They were then subjected to either sham operations, ablation of the marginal and splenial gyri, or lesions in the extramarginal (EM) cortex. The 32 EM cats comprised 4 groups, 3 with small (EM1), intermediate (EM2), large (EM3) decortications, and a 4th group with both EM lesions and heavy degeneration in the lateral geniculate nucleus (LGN). Ss with marginal or extensive extramarginal lesions were severely impaired in shape and size discrimination. Results show the following: (a) The errors made by marginal gyrus cases increased sharply as a function of the number of irrelevant cues present in shape discrimination training; no other group, including Group EM3, was affected by this variable. (b) Ss with extramarginal ablations and strong LGN degeneration were no more severely impaired than were Ss with comparable extramarginal damage and little or no LGN degeneration. While the nature of the 2 kinds of deficits remains unclear, they seem parallel to those following posterior cortical lesions in monkeys. (PsycINFO Database Record (c) 2010 APA, all rights reserved)