The differential effects of additional cortical lesions in rats with single- or multiple-stage lesions of the visual cortex

Abstract

Male albino rats relearned a black-white discrimination for food after posterior neocortex was bilaterally removed in a single operation (“single stage”) or in two unilateral operations (“multiple stage”). Single-stage animals showed no savings in relearning (relearning errors = learning errors). Multiple-stage animals showed positive savings (relearning errors < learning errors). To assess cortical reorganization, the rats were given additional lesions and again retrained. Cortex either contiguous or noncontiguous with the posterior lesion was removed bilaterally. Contiguous and noncontiguous lesions produced different effects only among animals with prior multiple-stage posterior lesions. Rats with single-stage posterior lesions and contiguous or noncontiguous lesions showed positive savings and did not differ from each other or from rats with multiple-stage posterior and noncontiguous lesions. Rats with multiple-stage posterior and contiguous lesions made more errors and showed negative savings. The role of contiguous cortex in the serial lesion effect was also tested with two additional groups. Rats given noncontiguous cortex lesions prior to multiple-stage posterior lesions showed positive savings in retraining. Rats given contiguous cortex lesions prior to multiple-stage posterior lesions showed negative savings. © 1977, Psychonomic Society, Inc.. All rights reserved.