The habenula is part of the epithalamus and receives input from the brain via the stria medullaris. It outputs to many midbrain areas involved in releasing neuromodulators, such as dopamine, norepinephrine, and serotonin.
The habenula was traditionally divided into lateral (limbic) and medial (motor) parts although the lateral part should be further divided into ten distinct subnuclei and the medial into five distinct subnuclei.
It has many functions, including pain processing, reproductive behavior, nutrition, sleep-wake cycles, stress responses, and learning. Functional MRI (fMRI) has recently linked the function of the lateral habenula with reward processing, in particular with regard to encoding negative feedback or negative rewards.