The Corpora Mamillaria

Anyone who has ever seen the corpus mamillare of the brain knows why they are called that – “mamilla” is Latin for small breasts. They are located at the base of the brain, the diencephalon, to be precise. However, they are not flanked by armpits and shoulders, as breasts should be. No, the structures that border them on the right and left are called the cerebral peduncles, or crura cerebri – “crura” meaning shanks in Latin. Well-rounded breasts – but between the thighs. Another drawback: the nipples are missing.

Anatomically speaking, the mammillary bodies belong to the diencephalon, and specifically to the hypothalamus, whose posterior section they form. Functionally, they are part of the limbic system, which comprises numerous structures of the diencephalon and telencephalon.

Based on the relatively little we know about them, the mammillary bodies are little more than switching stations in which almost no information processing takes place. Most of the axons that terminate in the mammillary bodies originate in the hippocampus, or more precisely, in its subiculum, via the fornix. The neurons of the mamillary bodies send their axons to the anterior thalamic nuclei, which in turn send theirs to the cingulate gyrus of the cortex, which then sends its axons to the entorhinal cortex and the hippocampal formation. This results in a loop known as the Papez circuit of the limbic system. This neural circuit plays a key role in the storage of new memory content. In addition, there is a connection between the mammillary bodies and the nuclei of the tegmentum, i.e., the midbrain, the function of which is not yet fully understood.

As mentioned above, the function of the Papez circuit is well known, and if this circuit is interrupted, massive memory disorders occur – content is only retained for a few minutes, the formation of new memories is impossible, and life becomes an eternal present. Unfortunately, damage to the mamillary bodies is not uncommon. As doctors say in their inimitable jargon, they are “selectively vulnerable to ethyl toxic insult.” To put it in terms that everyone can understand (especially those affected): you can drink it away. It is only a minor detail that the culprit is not so much the alcohol itself as the chronic vitamin B1 deficiency often found in alcoholics. This affects the nerve cells of the mamillary bodies.

Their destruction can have other effects: so-called confabulations – confused, fabricated stories with which those affected try to cover up their memory gaps from themselves and the world. However, those affected are not aware that these are confabulations – they would swear at any time that their own statements are correct.
 

Footnote: Curious naming

If you leaf through the various classics of anatomy – Prometheus, Terminologia anatomica/International Anatomical Terminology from the Federative Committee on Anatomical Terminology (FACT) – you will find different spellings – sometimes mamillaria with one “m” and sometimes mammillaria. This second “m” determines whether the original name refers to “breast” or “nipple” (mamille). Our author originally adhered to the FACT, but after various discussions, we decided to remove one “m.” Google does the same, and ultimately, we want this text to be found.

However, the question of breast or nipple remains open. Take a look at some pictures on the internet – and decide for yourself.

First published on August 23, 2011
Updated on November 28, 2025