The Hippocampus - Neurotransmission and Plasticity in the Nervous System the Hippocampus - Neurotransmission and Plasticity in the Nervous System

The hippocampus (Greek. hippos, horse, and kampe, curve) is a highly distinctive and structured region of the brain. It is a compact, elongated and incurved structure, with a seahorse shape after which it is named. There are two hippocampi, located on each side of the brain. They lie beneath the neocortex, on the basal medial surface of the temporal lobes. The hippocampi are anatomically simpler than most other areas of the central nervous system (CNS). They are composed of two regions: the dentate gyrus (DG) and Cornu Ammonis (CA). The CA region is divided into four subfields, CA1, CA2, CA3 and CA4. The DG and CA contain a principal cell layer, the granule and pyramidal cell layers respectively. The hippocampi have a unique pattern of connectivity; a tri-synaptic circuit organized in lamella along their septotemporal axis. The entorhinal cortex represents the main afference of the hippocampus. The entorhinal cortex and hippocampus are an important memory center of the brain.