Mammillary body

The mammillary bodies (mamillary bodies) are a pair of small round bodies, located on the undersurface of the brain, that, as part of the diencephalon form part of the limbic system. They are located at the ends of the anterior arches of the fornix. They consist of two groups of nuclei, the medial mammillary nuclei and the lateral mammillary nuclei. Neuroanatomists have often categorized the mammillary bodies as part of the hypothalamus.

Connections
They are connected to other parts of the brain (as shown in the schematic, below left), and act as a relay for impulses coming from the amygdalae and hippocampi, via the mamillo-thalamic tract to the thalamus.

This circuit, from amygdalae to mammillary bodies, and then on to the thalamus, is part of the larger 'Papez circuit'.

Function
They, along with the anterior and dorsomedial nuclei in the thalamus, are involved with the processing of recognition memory.

They are believed to add the element of smell to memories.

Pathology
Damage to the mammillary bodies due to thiamine deficiency is implied in pathogenesis of Wernicke-Korsakoff syndrome. Symptoms include impaired memory, also called anterograde amnesia, suggesting that the mammillary bodies may be important for memory. Lesions of the medial dorsal and anterior nuclei of the thalami and lesions of the mammillary bodies are commonly involved in amnesic syndromes in humans.