The Human Brain : From Neurone to Nervous System

THE HIPPOCAMPUS : STRUCTURE and FUNCTION


  1. The hippocampus is the cortical area concerned with formation and recall of memories; it also has a role in emotional behaviour.
    The adjacent entorhinal (parahippocampal) cortex and subiculum communicate with the hippocampus and the closely associated dentate gyrus. It has a role to play is spatial navigation.

  2. The hippocampus and dentate gyrus are shaped like interlocking 'C's and, unlike most areas of cerebral cortex, both have only three layers.

  3. Axons from the superficial layers of the entorhinal cortex project through a three-neurone circuit that returns information from the hippocampus back to the deeper layers of the entorhinal cortex. The cells in this 3-neurone circuit are
    • granule cells in the dentate gyrus, whose axons, 'mossy fibres', project to
    • pyramidal cells in area CA3 of Ammon's Horn (Cornus Ammonis), that connect with
    • pyramidal cells in area CA1, which send signals back to the deeper layers of the entorhinal cortex.

  4. The pyramidal cells of CA1 have an ability to alter synaptic efficacy by trafficking more receptors into the post-synaptic membrane during repetitive activity, a process called long term potentiation (LTP), believed to be associated with short term memory.

  5. The subgranular layer of neurones in the dentate gyrus is the site of production of new neurones in adults; it has been suggested that adult neurogenesis may be involved in the laying down of long term memories.

  6. Key Words: Hippocampus, Entorhinal Cortex, Dentate Gyrus, Sub-Granular Zone, Amygdala.







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