Hippocampus
Also known as: hippocampi
A small, seahorse-shaped structure in the temporal lobe of each hemisphere — central to memory formation and spatial navigation.
The hippocampus is a paired structure (one in each hemisphere) tucked into the medial temporal lobe. The name comes from its resemblance to a seahorse — hippokampos in Greek.
It is one of the most-studied regions in neuroscience because of its central role in:
- Episodic memory — forming and consolidating memories of events
- Spatial navigation — the famous "place cells" of John O'Keefe were first recorded in the hippocampus
- Pattern separation — distinguishing similar experiences from one another
Why it's measured in neuroimaging
Hippocampal volume is one of the most sensitive imaging biomarkers we have:
- It shrinks measurably in Alzheimer's disease, often years before clinical symptoms
- It is affected in chronic stress and depression
- It is one of the few brain regions where adult neurogenesis appears to occur, making it relevant for studies of exercise, learning, and recovery
In a typical volumetric analysis, the left and right hippocampi are reported as absolute volumes (mm³) and as percentages of estimated total intracranial volume (eTIV), which corrects for individual differences in head size.
In our work
Hippocampal volume is part of the standard volumetric panel in our neuroimaging analytics service.
Related terms
Brain age
An estimate of how old your brain appears structurally compared to a healthy reference population, derived from a single MRI scan.
Cortical thickness
The thickness of the brain's outer grey-matter ribbon (the cortex), measured millimetre-by-millimetre across its surface from a structural MRI.