Median raphe nucleus

The median raphe nucleus (MRN or MnR), also known as the nucleus raphes medianus (NRM) or superior central nucleus, is a brain region composed of polygonal, fusiform, and piriform neurons, which exists rostral to the nucleus raphes pontis. The MRN is located between the posterior end of the superior cerebellar peduncles and the V. Afferents of the motor nucleus. It is one of two nuclei, the other being the dorsal raphe nucleus (DnR), in the midbrain-pons.

The MRN projects extensively to the hippocampus, which is known to be essential for the formation of long-term memory. One recent study found that this raphe–hippocampus pathway plays a critical role in regulation of hippocampal activity and likely associated memory consolidation processes. It has also been found to play a role in anxiety and depression, as one of the few parts of the brain that creates tryptophan hydroxylase.