Habenula

In neuroanatomy, habenula originally denoted the stalk of the pineal gland (pineal habenula; pedunculus of pineal body), but gradually came to refer to a neighboring group of nerve cells with which the pineal gland was believed to be associated, the habenular nucleus. Currently, the Terminologia Anatomica term refers exclusively to this separate cell mass in the caudal and dorsal aspect of the dorsal thalamus, the epithalamus, embedded in the posterior end of the medullary stria from which it receives most of its afferent fibers. By way of the retroflex fasciculus (habenulointerpeduncular tract) it projects to the interpeduncular nucleus and other paramedian cell groups of the midbrain tegmentum. Despite its proximity to the pineal stalk, no connecting tissue is known to exist.

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The habenula is involved in receiving input from the brain via the stria medullaris thalami and output to many midbrain areas involved in releasing personality-related neurotransmitters and neuromodulators, such as dopamine, norepinephrine, and serotonin (from the ventral tegmental area, locus coeruleus and raphe nucleus respectively.)

The habenula is the only nucleus of the epithalamus.