Part of the diencephalon, the mamillary bodies are a pair of nuclei that are each divided into lateral and medial subnuclei. The medial subnuclei is larger. The mammillary bodies are connected to the hippocampus via the fornix, thalamus via the mammillothalamic tract, and midbrain tegmentum via the mammillary peduncle and mammillotegmental tract. They play a key role in memory consolidation and maintaining a sense of direction.