MICROINJECTION OF GABA-A AGONIST MUSCIMOL INTO THE DORSAL BUT NOT THEVENTRAL HIPPOCAMPUS IMPAIRS NON-MNEMONIC MEASURES OF DELAYED NON-MATCHING-TO-POSITION PERFORMANCE IN RATS

Anatomical studies of afferent and efferent connections suggest that t he hippocampus may have more than one information processing role that varies along the septo-hippocampal axis. The present study was conduc ted to test whether a distinct functional specialization for the dorsa l versus ventral extents of the hippocampus could be detected. The eff ects of a GABA-A receptor agonist, muscimol, microinjected into either the dorsal or ventral hippocampus on an operant, spatial delayed non- matching-to-position (DNMTP) task were measured. A decrease in the num ber of trials completed per session and disruption of several DNMTP di scrimination parameters were produced by muscimol microinjected into t he dorsal hippocampus but not into the ventral hippocampus. Muscimol i njected into either site did not impair the measure of working memory, delayed choice accuracy. These results are consistent with the view t hat hippocampal function varies along the septo-temporal axis, and tha t the dorsal hippocampus is relatively more critical to visual discrim ination performance than the ventral hippocampus. (C) 1998 Elsevier Sc ience B.V.