Hippocampal overshadowing : exploring the underlying mechanisms

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Gulbrandsen, Tine L
University of Lethbridge. Faculty of Arts and Science
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Lethbridge, Alta. : University of Lethbridge, Dept. of Neuroscience
The aim of the current thesis was to evaluate the underlying mechanisms of hippocampal (HPC) overshadowing. One theory to explain this phenomenon predicts that perceptual representation of an event is stored in non-HPC cortical areas. Following multiple distributed exposure to the same or similar event, this representation becomes stable and the cellular activation patterns can be recalled in the absence of HPC input. Through a series of experiments, the hypothesis that the dysgraunlar layer of the retrosplenial cortex (RSD) fulfill these requirements was tested. Using double in-situ hybridization for the mRNA of immediate-early genes Arc and Homer1a, the cellular activation patterns in HPC subregion CA1 and RSD were evaluated. In addition, temporary inactivation of HPC was used to evaluate cellular activation patterns of a HPC-independent memory in RSD. The results presented here support the idea that cellular activation patterns for may be stored – at least in part – in the RSD.
hippocampus , learning , memory , overshadowing