Retrograde amnesia and memory reactivation in rats with ibotenate lesions to the hippocampus or subiculum.

Johan J. Bolhuis, Caroline A. Stewart, Elma M. Forrest

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    119 Citations (Scopus)


    The retrograde effects of hippocampal lesions on spatial memory were studied. Rats were given a series of 48 place-navigation trials in an open-field water-maze followed, either 3 days or 14 weeks later, by ibotenic acid lesions of the hippocampus (HPC) or subiculum (SUB), or by sham-surgery (SHAM). Two weeks after surgery they were given a retention test without a hidden escape platform. There was a significant decline in performance with time in the SHAM group, but with the 14-week SHAM group performing significantly better than chance levels, whereas both lesioned groups performed at chance at both retention intervals. All rats were then retrained for 24 trials. SHAM rats escaped rapidly within 2 trials, suggesting a reactivation of memory rather than relearning. The HPC groups were severely impaired during retraining, with a developing trend towards better performance in the 3-day group. After 24 trials of training with the escape platform placed in the opposite quadrant of the pool, this new location was learned successfully by SHAM and SUB rats, but not by HPC rats. These results indicate that selective hippocampal formation lesions can cause deficits in retrieval but do not reveal a time-dependent gradient of memory consolidation.
    Original languageEnglish
    Pages (from-to)129-150
    Number of pages22
    JournalQuarterly Journal of Experimental Psychology Section B: Comparative and Physiological Psychology
    Issue number2
    Publication statusPublished - 1 May 1994


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