Effects of hippocampal lesions to the lever-press responses on the discrimination learning in rat

• Published in: Japanese Journal of Pharmacology 1998, Vol.76 (suppl.1), p.153-153
• Main Authors: Matsumoto, Akira, Kubo, Taizo, Gogi, Akiko, Ishikawa, Koichi
• Format: Article
• Language: English
• ISSN: 0021-5198; 1347-3506
• DOI: 10.1016/S0021-5198(19)40721-X

The aim of this experiment is to investigate that the hippocampal system is necessary to the configural association in rats. Animals were trained to a discrimination learning in which the lever-press was rewarded with a chow for the light([L+]) and/or tone([T+]) alone but was not for a combined([LT-]) stimulus. Each trial was followed by an intertrial interval(ITI). The hippocampal lesion was produced by the local injection of kainate and colchicine prior to the beginning of trainings or retention test. The lesioned rat was impaired both acquisition and retention of [L+]/[T+]/[LT-] discrimination learnings and caused an increase of the response numbers in ITIs. All ITI responses were divided the rewarded(R) from non-rewarded(non-R) trials and both divisions were further distinguished between correct(C) and error(E) responses for presented stimuli. ITI responses were mainly presented in two divisions of R-C and non-R-E in early sessions and trainings have removed the distribution from non-R-E to non-R-C although R divisions did not. The hippocampal lesions were significantly increased ITI responses of both E divisions, especially non-R-E, in comparison to control. These results suggest that the increase of ITI responses was caused by the impairment of learning and memory in rats with hippocampal lesions and the hippocamus actively participated in memory formations of configural association.