Hippocampus: Intrinsic Organization

Peter Somogyi

in Handbook of Brain Microcircuits

Published on behalf of Oxford University Press

Published in print August 2010 | ISBN: 9780195389883
Published online September 2012 | e-ISBN: 9780199965137 | DOI:
Hippocampus: Intrinsic Organization

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The hippocampus (CA1, CA2, and CA3 areas and the dentate gyrus), together with the subiculum, represents an associational area of the cerebral cortex intimately involved in mnemonic processes. Through its connections with other areas of the temporal lobe, the hippocampus contributes to the encoding, association, consolidation, and recall of representations of the external and internal world in the combined firing rates and spike timing of glutamatergic pyramidal and granule cells. The hippocampus is thought to associate specific life events (items, episodes), on several time scales, in temporally determined firing sequences of neuronal assemblies. A single pyramidal cell can be part of several cell assemblies with different partners and contribute to different representations. Pyramidal cell assemblies are thought to be kept together and segregated from other assemblies by the dynamic strengthening and weakening of glutamatergic synaptic weights as well as by GABAergic interneurons. Interneurons generate cell domain and brain state-dependent rhythmic changes in excitability, which are key for the formation, consolidation, and recall of representations. Unsurprisingly, interneurons show intricate spatiotemporal diversity; for example, the CA1 area is served by at least twenty-one types of resident GABAergic cell. This chapter attempts to allocate explicit roles for some of them, based on their previously published firing patterns in vivo as observed in identified neurons recorded in anesthetized rats and on their putative equivalents in nonanesthetized animals.

Chapter.  6177 words.  Illustrated.

Subjects: Development of the Nervous System

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