Role of cortex in Pavlovian discrimination learning.

Two totally neodecorticate rabbits and two groups of normal rabbits were trained on a light-tone differentiation using a Pavlovian nictitating membrane response. The significance of the two stimuli involved in the differentiation was then reversed. Excellent initial differentiations were produced by both decorticates and normals, although there was some evidence of a small retardation of conditional response acquisition in the decorticates in this first stage of the experiment. Under reversal conditions the decorticates extinguished responding to the formerly positive conditional stimulus in fewer trials and produced more complete differentiation performances than normal animals. The decorticates, unlike the normal animals, failed to show a reduction in conditional response onset latencies during either differentiation or reversal training.