Habenula

Habenula
Mesal aspect of a brain sectioned in the median sagittal plane. Habenula is not labeled directly, but after expanding, look to region with 'habenular commissure', 'pineal body', and 'posterior commissure'
Taenia choroidea (and lateral: Lamina affixa, Stria terminalis) Thalamus, Pulvinar thalami Third ventricle Stalk of pineal gland Habenula Stria medullaris Superior colliculus Brachium of superior colliculus Inferior colliculus Brachium of inferior colliculus Medial geniculate nucleus Sulcus medianus Superior cerebellar peduncles Inferior cerebellar peduncle Middle cerebellar peduncles Tuberculum anterius thalami Obex, Area postrema
Identifiers
MeSH	habenula
NeuroNames	hier-277
NeuroLex ID	Habenula
Dorlands /Elsevier	h_01/12405682
TA	A14.1.08.003
FMA	62032
Anatomical terms of neuroanatomy []

In neuroanatomy, habenula (diminutive of Latin habena meaning rein) 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. The habenular nucleus is a set of well-conserved structures in all vertebrate animals.

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 fasciculus retroflexus (habenulointerpeduncular tract) it projects to the interpeduncular nucleus and other paramedian cell groups of the midbrain tegmentum.

The habenula receives input from the brain via the stria medullaris thalami and outputs to many midbrain areas involved in releasing neurotransmitters, such as dopamine, norepinephrine, and serotonin.

The habenula was traditionally divided into lateral (limbic) and medial (motor) parts. Detailed examination of the region in the cat, however, suggested that the lateral part should be further divided into ten distinct subnuclei and the medial into five distinct subnuclei.

The primary input regions to the lateral habenula are the lateral preoptic area (bringing input from the hippocampus and lateral septum), the ventral pallidum (bringing input from the nucleus accumbens and mediodorsal nucleus of the thalamus), the lateral hypothalamus, the medial habenula, and the internal segment of the globus pallidus (bringing input from other basal ganglia structures).