The hippocampus is a seahorse shaped structure in the medial temporal lobe that is central to forming and retrieving memories, navigating space, and regulating emotional responses. Research shows it acts as a hub that binds together “what, where, and when” information into coherent episodic memories. Damage to the hippocampus does not erase old memories but severely impairs the formation of new long term memories.

Within the hippocampus, place cells fire when an animal is in a specific location, forming an internal map of the environment. These cells work with grid cells in nearby cortex to support spatial navigation and context dependent memory. The hippocampus is also involved in imagining future events, suggesting that it helps recombine stored elements into mental simulations.

Synaptic plasticity in hippocampal circuits, especially long term potentiation, is a major cellular mechanism thought to underlie learning. Strengthening or weakening of synapses adjusts how information flows through its distinct subregions, such as the dentate gyrus and CA fields, enabling pattern separation and pattern completion. This allows the brain to distinguish similar experiences while also retrieving complete memories from partial cues.

The hippocampus is sensitive to stress and biological rhythms. Chronic stress and high glucocorticoid levels can reduce its volume and impair memory, while sleep and memory replay during slow wave and REM stages appear crucial for consolidating hippocampal dependent memories. In humans, hippocampal dysfunction is implicated in conditions such as Alzheimer’s disease, post traumatic stress disorder, depression, and temporal lobe epilepsy, making it a key focus of both basic neuroscience and clinical research.