Hippocampus, Spatial Memory, and Neuroimmuomodulation

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 subregions: 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 the hippocampus is its connection circuitry. The connections within the hippocampus generally follow this laminar format and they are largely unidirectional. They form well-characterized closed loops that originate mainly in the adjacent entorhinal cortex. Thus, information flows through the hippocampus proceeds from the dentate gyrus to CA3–CA1 to the subiculum, forming the principal tri-synaptic 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 formation/retrieval of memories. In addition, the hippocampus is also involved in neuromodulation and neuroinflammation. Overall, the hippocampus plays a crucial role in both cognitive function and immune regulation, highlighting the interconnectedness of various systems in the body.