Side by side
| Compared | Hippocampus | Amygdala |
|---|---|---|
| Where it is | In the medial temporal lobe of each hemisphere: a curved fold of three-layered cortex (archicortex) that bulges into the floor of the lower (inferior) horn of the lateral ventricle. [1] | Medially within each temporal lobe: a nuclear complex, a cluster of grey-matter nuclei inside the hemisphere rather than a fold of cortex. [2] |
| What it does | Consolidates information from short-term memory into long-term memory, and supports spatial memory, the memory that lets you navigate. [1] | Processes memory, decision-making and emotional responses; it plays a role in expressing fear and in processing fear-inducing stimuli. [2] |
| Connects with | Main input from the entorhinal cortex; main output through the fornix, whose fibres run on through the hypothalamus to the mammillary bodies. [5][6] | Its basolateral complex links with prefrontal, temporal and insular cortex and with the hippocampus; its central nucleus projects to the brainstem; its cortical and medial nuclei connect with the smell system and the hypothalamus. [2] |
| Size measured from the model | 43 mm front to back, 22 mm top to bottom, 20 mm side to side [4] | 18 mm front to back, 13 mm top to bottom, 17 mm side to side [4] |
Size is the box each part fits in on this one model (left hippocampus; left amygdala), not its volume. Real brains vary. A part that comes as a left and a right copy is measured on its left copy; the right one mirrors it.
How far apart are they?
Measured from the model [4], from the left hippocampus to the left amygdala:
- Centre to centre: 20 mm in a straight line.
- The centre of the left amygdala is 20 mm further forward, level top to bottom and 1 mm closer to the midline than the centre of the left hippocampus.
- Nearest points of the two shapes: under 1 mm apart.
A “centre” here is the average position of the points on the part’s 3D surface, so for a curved part such as a C shape it can sit outside the part itself. The nearest-points figure is measured between the corners of the simplified meshes, so a gap of 2 or 3 mm or less is within the model’s coarseness: read it as “touching or nearly so”.