Hippocampus: structure, function, and clinical roles

Hippocampus overview and major roles

The hippocampus is a major brain structure in humans and other vertebrates, located in the medial temporal lobe and part of the limbic system. In the hippocampal formation, it works with the dentate gyrus and subiculum and is strongly connected with the neocortex via the entorhinal cortex. It is especially important for consolidating information from short-term memory into long-term memory and for spatial memory that supports navigation. Anatomically, the hippocampus is an inward fold of layered archicortex and is organized along two main axes: an anterior–posterior (head–body–tail) axis and a proximal–distal axis that includes subfields such as CA1–CA4 and the dentate gyrus. Functionally, it is studied as a model for neurophysiology because it exhibits well-characterized plasticity, including long-term potentiation (LTP), which is widely believed to be a mechanism for memory storage. Neurons in rodents show “place cell” activity, firing when an animal is in specific locations, and this spatial coding interacts with other navigation-related cell types. Physiologically, hippocampal activity shows distinct modes such as theta rhythms during active behavior and REM sleep, and sharp waves (with associated ripples) during slow-wave sleep and rest. Sharp waves are strongly linked to memory processes, including reactivation of place-cell activity and theories proposing that hippocampal activity during behavior is later replayed during sleep. Clinically, early hippocampal damage is common in Alzheimer’s disease and can produce anterograde amnesia, while other conditions such as hypoxia, encephalitis, and medial temporal lobe epilepsy can also impair hippocampal function.

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Hippocampal formation components

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