Hippocampus, spatial memory and neuroimmunomodulation

The hippocampus is a symmetrical structure located inside the medial temporal lobe on both sides of the human brain. In cross-sections, the hippocampus consists of two interlocking sheets of cortex with three distinct sub-regions: the dentate gyrus, the hippocampus proper (CA1-CA3) and the subiculum. The hippocampus has a much defined laminar structure with layers visible where rows of pyramidal cells are arranged. A striking feature of hippocampus is its connection circuitry. The connections within the hippocampus generally follow this laminar format and are largely unidirectional. They form well-characterized closed loops that originate mainly in the adjacent entorhinal cortex. Thus information flow through the hippocampus proceeds from dentate gyrus to CA3 to CA1 to the subiculum, forming the principal trisynaptic circuit. Together with the adjacent amygdala and entorhinal cortex, the hippocampus forms the central axis of the limbic system and plays an important role in spatial learning and awareness, navigation, and episodic/event memory. In addition, the hippocampus plays a role in neuroimmunomodulation.