Hippocampus

Part of the brain involved in memory and navigation

The hippocampus is a major component of the brain of humans and other vertebrates. It belongs to the limbic system and plays important roles in the consolidation of information from short-term memory to long-term memory, and in spatial memory that enables navigation.

Diagram of the human brain with the hippocampus highlighted.

Anatomy

The hippocampus is located in the medial temporal lobe of the brain, underneath the cortical surface. It has a distinctive curved shape that has been likened to a seahorse, which is reflected in its name derived from the Greek words "hippos" (horse) and "kampos" (sea monster).

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The hippocampus is named for its resemblance to a seahorse.

The hippocampus consists of two main interlocking parts: the Ammon's horn and the dentate gyrus. The Ammon's horn is further divided into subfields CA1, CA2, CA3, and CA4, each with distinct cellular compositions and functions.

Function

The primary function of the hippocampus is in the formation of new memories and is also associated with learning and emotions. It is particularly important for declarative memory, which involves facts and events, and spatial memory, which involves the ability to navigate and remember locations.

The hippocampus is part of the limbic system, shown here in a diagram of the human brain.

Memory

The hippocampus is crucial for the formation of new memories. Damage to the hippocampus can result in anterograde amnesia, where the ability to form new memories is impaired, while older memories remain intact.

Spatial Navigation

The hippocampus is involved in spatial navigation and memory. It helps in the formation of cognitive maps, which are mental representations of physical locations.

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Rats use their hippocampus to navigate mazes, forming cognitive maps.

Pathology

Damage to the hippocampus can result from various conditions, including Alzheimer's disease, hypoxia, encephalitis, or temporal lobe epilepsy. Such damage can lead to memory deficits and difficulties in spatial navigation.

Research

Research on the hippocampus has been extensive, with studies ranging from its role in memory and learning to its involvement in neurogenesis and plasticity. The hippocampus is one of the few regions of the brain where new neurons are generated throughout life.

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Early anatomical drawing of the hippocampus.

Comparative Anatomy

The structure and function of the hippocampus are conserved across many species, including mammals, birds, and reptiles. In macaques, the hippocampus is similarly involved in memory and spatial navigation.

Hippocampus in a macaque brain.

Historical Perspective

The study of the hippocampus has a rich history, with significant contributions from scientists such as Santiago Ramón y Cajal, who provided detailed drawings of its structure.

Drawing of the hippocampus by Santiago Ramón y Cajal.

Neuroanatomy

The hippocampus is part of the archicortex, one of the oldest parts of the brain in evolutionary terms. It is connected to other parts of the brain through the fornix and receives input from the entorhinal cortex.

Coronal section of the hippocampus.

Related pages

• Limbic system
• Memory
• Spatial memory
• Neurogenesis
• Cognitive map