Mammillary body

The mammillary bodies are a pair of small round bodies, located on the undersurface of the brain, that form part of the limbic system. They are located at the ends of the anterior arches of the fornix, and are named mammillary for their resemblance to two breasts. 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.^[1]

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 mamillary bodies, and then on to the thalamus, is part of the larger ‘Papez circuit‘.

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

The mammillary bodies are parts of the brain known to be significantly damaged by alcohol intoxication, especially by chronic alcohol abuse and associated deficiency of thiamine. Researchers, in 1998, also noted visible abnormalities in the mammillary bodies of individuals with autism.^[2]

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.^[3]

• Vann S, Aggleton J (2004). “The mammillary bodies: two memory systems in one?” (PDF). Nat. Rev. Neurosci. 5 (1): 35–44. PMID 14708002.
• TheFreeDictionary.com – ‘Mammillary body’
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