Where it is
- It forms a horizontal ridge on the medial surface of the thalamus, on the border between its upper (dorsal) and medial surfaces. [1]
- It emerges as a compact bundle on each side just behind the anterior commissure, where it meets the fornix and the stria terminalis. [1]
- It runs back along the roof of the third ventricle, arching over the thalamus (in most people above the interthalamic adhesion), then descends to end in the habenula. [1]
- It is part of the epithalamus, the back (dorsal) part of the diencephalon that also holds the habenular nuclei, the posterior commissure and the pineal gland; with the habenula and the habenular commissure it forms the habenular trigone. [1][2]
What it does
- It is the main input route of the habenula: it gathers fibres from frontal, septal, striatal and hypothalamic areas and carries them, mostly one way, to the lateral and medial habenulae. [1]
- The habenula it feeds has a medial and a lateral part on each side, joined across the midline by the habenular commissure; the lateral habenula has been closely linked with reward processing, in particular with signalling negative feedback or a reward that does not come. [3]
- Its inner fibres bend in towards the base of the pineal gland, cross to the other side and end in the opposite habenula; this crossing is the habenular commissure. [1]
- The signals it carries in are mainly cholinergic, glutamatergic and GABAergic. [1]
- Honest limit: it is so bound up with the habenula that a function of its own is hard to define, and it was once even thought to be part of the smell (olfactory) system. [1]
Connections
- It is the first part of the dorsal diencephalic conduction system (DDCS) and is considered that system’s main input. [1]
- Its fibres come from the septal nuclei, the lateral preoptic and hypothalamic region and the anterior thalamic nuclei. [1]
Inside it
- White matter: a tract of nerve fibres, one on each side. [1]
Other names
- Also called the stria medullaris thalami or the habenular stria; older names include columna medullaris. Vesalius drew it in 1543, and it got its present name from Wenzel and Wenzel in 1812. [1]
Size
- On this model the left stria medullaris of thalamus measures about 37 mm front to back, 16 mm top to bottom and 4 mm side to side (the box it fits in, not its volume); the right one is its mirror image. [4]
- Centre of the left stria medullaris of thalamus compared with the centre of the habenula: 16 mm further forward, 7 mm higher; 18 mm apart in a straight line. [4]