DISRUPTION OF SPATIAL BUT NOT OBJECT-RECOGNITION MEMORY BY NEUROTOXICLESIONS OF THE DORSAL HIPPOCAMPUS IN RATS

Ischemia-induced cell loss in the CAI region of thr dorsal hippocampus results in severe deficits on delayed non-matching-to-sample (DNMS), whereas hippocampectomy produces little or no impairment, suggesting t hat partial hippocampal damage is more detrimental to DNMS performance than total ablation. To test this hypothesis, rats with or without pr eoperative DNMS training were given partial cytotoxic lesions of the d orsal hippocampus. When tested. neither group displayed any DNMS defic its despite widespread cell loss in the CA1 and other regions of the d orsal hippocampus. In the final experiments, rats tested previously on DNMS were found to be impaired on the Morris water maze. The finding that partial hippocampal lesions disrupt spatial memory while leaving object-recognition memory intact indicates a specialized role for the hippocampus in mnemonic processes.