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Critical role of the hippocampus in memory for sequences of events


Recent models of hippocampal function emphasize the potential role of this brain structure in encoding and retrieving sequences of events that compose episodic memories. Here we show that hippocampal lesions produce a severe and selective impairment in the capacity of rats to remember the sequential ordering of a series of odors, despite an intact capacity to recognize odors that recently occurred. These findings support the hypothesis that hippocampal networks mediate associations between sequential events that constitute elements of an episodic memory.

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Figure 1: Sequential order and recognition tasks.
Figure 2: Performance (mean percent correct ± s.e.m.) of control rats and rats with hippocampal lesions on sequential order memory task.
Figure 3: Performance (mean percent correct s.e.m.) of control rats and rats with hippocampal lesions on recognition for each of the different types of probes.
Figure 4: Comparison of performance on recognition and sequential order tests.
Figure 5: Hippocampal subdivisions affected by the lesions at three anterior–posterior levels.


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We thank S. Rubin, J. Tourigny, S. Wright, L. Griffith, A. Cahill and A. Ceriales for help with behavioral testing and histological work. Supported by NIMH MH52090 (H.B.E.), NIA AG09973 (H.B.E.), and NSERC (N.J.F.).

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Correspondence to Howard B. Eichenbaum.

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Fortin, N., Agster, K. & Eichenbaum, H. Critical role of the hippocampus in memory for sequences of events. Nat Neurosci 5, 458–462 (2002).

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