Learning and extinction during chemically induced disturbance of hippocampal functions

Abstract

Potassium chloride was introduced into the hippocampi of rats to study the effects of a persisting but reversible disturbance of hippocampal functions on the acquisition, performance, and extinction of a black-white discrimination habit in a T maze apparatus. Acquisition and retention, as measured by the percentage of correct choices, were not affected by the disruption of hippocampal functions. However, an analysis of the temporal parameters of the discrimination response (start, running, choice, and total response speed) demonstrated significant performance deficits during acquisition as well as at the asymptote of performance. The correct choice as well as the latency measures reflected this impairment during extinction. The results are interpreted to suggest that an interference with hippocampal functions may affect performance variables such as motivation rather than associative mechanisms specifically related to acquisition or retention.