Maintenance and Behavioural Expression of Long-term Memories Acquired in the Absence of the Hippocampus

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Gidyk, Darryl C.
University of Lethbridge. Faculty of Arts and Science
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Lethbridge, Alta. : University of Lethbridge, Dept. of Neuroscience
We examine the maintenance and behavioural expression of long-term memories acquired in the absence of the hippocampus. The hypothesis that the hippocampus is necessary to form stable and detailed long-term memories is tested. We find rats with extensive hippocampal damage made before learning exhibit normal maintenance and behavioural expression of contextual fear memory, object discrimination, and context discrimination. The discovery that non-hippocampal networks can encode, maintain, and retrieve memories, widely-thought to be dependent on the hippocampus and its consolidation processes adds to a growing body of literature which draws into question most views of the hippocampus and memory consolidation. Our findings suggest: 1) hippocampal-dependent systems-level consolidation is not required for stable long-term memory in the rat; 2) non-hippocampal networks possess sufficient representational complexity to support normal discriminative memory-guided behaviours; 3) the broad distinction between hippocampal and non-hippocampal memories requires re-evaluation through rigorous experimentation, rather than adherence to modal views.
Hippocampus (Brain) , Long-term memory