The subcortical region of the brain known as the hippocampus is horseshoe shaped, receiving its name from its similarity to the seahorse. Part of the limbic system, the hippocampus plays a significant role in emotion and sexuality, as well as memory and spatial comprehension. Featured below is a digital image of the hippocampus that was triple labeled (glia in orange, neurofilaments in green, and nuclei in blue). The image was captured using a 2-photon microscope.

Hippocampus Specimen: Fluorescently labeled thin section Technique: Two-Photon Microscopy

Studies have shown that damage to the hippocampus prevents subjects from making new memories. Although a person may be able to clearly remember their first day of school, if they have suffered trauma to the hippocampus, they would not be able to remember where they placed their glasses or what they ate for breakfast. However, sufferers of this variety of brain injury are able to learn new skills, such as tennis or golf. Each time they take part in the activity their skills improve, although they do not remember ever having attempted the game before.

The hippocampus is capable of neurogenesis, or growth of neurons, which scientists believe is intimately involved with the process of new memory formation. In studies of rats, the number of neurons generated in the hippocampi of subjects doubled after performing certain tasks involving associative learning. The research suggests, therefore, that utilizing the hippocampus helps maintain its health, a feature that may be important in attempts to forestall diseases characterized by hippocampus shrinkage, such as Alzheimer's.