The stria medullaris (SM), (Latin, furrow and pith or marrow) is a part of the

epithalamus The epithalamus (: epithalami) is a posterior (dorsal) segment of the diencephalon. The epithalamus includes the habenular nuclei, the stria medullaris, the anterior and posterior paraventricular nuclei, the posterior commissure, and the pine ...

and forms a bilateral white matter tract of the initial segment of the

dorsal diencephalic conduction system The epithalamus (: epithalami) is a posterior (dorsal) segment of the diencephalon. The epithalamus includes the habenular nuclei, the stria medullaris, the anterior and posterior paraventricular nuclei, the posterior commissure, and the pinea ...

(DDCS). It contains afferent fibers from the

septal nuclei The septal area (medial olfactory area), consisting of the lateral septum and medial septum, is an area in the lower, posterior part of the medial surface of the frontal lobe, and refers to the nearby septum pellucidum. The septal nuclei are loca ...

, lateral preoptico-

hypothalamic The hypothalamus (: hypothalami; ) is a small part of the vertebrate brain that contains a number of nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrine system via the pituit ...

region, and anterior thalamic nuclei to the

habenula The habenula (diminutive of Latin meaning rein) is a small bilateral neuronal structure in the brain of vertebrates, that has also been called a microstructure since it is no bigger than a pea. The naming as little rein describes its elongated ...

. It forms a horizontal ridge on the medial surface of the

thalamus The thalamus (: thalami; from Greek language, Greek Wikt:θάλαμος, θάλαμος, "chamber") is a large mass of gray matter on the lateral wall of the third ventricle forming the wikt:dorsal, dorsal part of the diencephalon (a division of ...

on the border between dorsal and medial surfaces of the thalamus. The SM, in conjunction with the

and the habenular commissure, forms the

habenular trigone The habenular trigone is a small depressed triangular area situated (sources differ) anterior/superior to the superior colliculus. It contains the habenular nuclei. Anatomy The habenular trigone is situated on the lateral aspect of the posterior ...

. It is considered to be the primary afferent of the DDCS.

History

Vesalius Andries van Wezel (31 December 1514 – 15 October 1564), Latinization of names, latinized as Andreas Vesalius (), was an anatomist and physician who wrote ''De humani corporis fabrica, De Humani Corporis Fabrica Libri Septem'' (''On the fabric ...

showed it in his 1543

De Humani Corporis Fabrica Libri Septem ''De Humani Corporis Fabrica Libri Septem'' (Latin, "On the Fabric of the Human Body in Seven Books") is a set of books on human anatomy written by Andreas Vesalius (1514–1564) and published in 1543. It was a major advance in the history of a ...

. It first received its present name from Wenzel and Wenzel in 1812. The SM can be referred to as the stria medullaris thalami or habenular stria. Historically it has also been called the ''columna medullaris'', ''markiger Streisen'' and ''rené''. It was once thought to be part of the olfactory system.

Anatomy

The SM emerges as a bilateral compact fascicle just posterior to the

anterior commissure The anterior commissure (also known as the precommissure) is a white matter nerve tract, tract (a bundle of axons) connecting the two temporal lobes of the cerebral hemispheres across the midline, and placed in front of the columns of the Fornix o ...

, where it converges with the fornix and

stria terminalis The stria terminalis (or terminal stria) is a structure in the brain consisting of a band of fibers running along the lateral margin of the ventricular surface of the thalamus. Serving as a major output pathway of the amygdala, the stria termina ...

. As it courses caudally along the third ventricle's roof, it attaches to the tela chordae and arches dorsally over the

. In the majority of individuals, it arches superior to the

interthalamic adhesion The interthalamic adhesion (also known as the massa intermedia, intermediate mass or middle commissure) is a flattened band of tissue that connects both parts of the thalamus at their medial surfaces. The medial surfaces form the upper part of th ...

. The SM then descends caudally, with its lateral fibers terminating in the

. The medial SM fibers, on the other hand, flex inwards towards the

pineal gland The pineal gland (also known as the pineal body or epiphysis cerebri) is a small endocrine gland in the brain of most vertebrates. It produces melatonin, a serotonin-derived hormone, which modulates sleep, sleep patterns following the diurnal c ...

's base, crossing to the opposite side and terminating in the contralateral habenula. This crossing is known as the

habenular commissure The habenular commissure is a nerve tract of commissural fibers that connects the habenular nuclei on both sides of the habenular trigone in the epithalamus. The habenular commissure is part of the habenular trigone (a small depressed triangula ...

Function

The SM primarily gathers fibers from various brain regions, including the frontal,

septal In biology, a septum (Latin for ''something that encloses''; septa) is a wall, dividing a cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate. Examples Human anatomy * Interatrial sep ...

, striatal, and

areas, and conveys information to the lateral and medial habenulae. It operates in a predominantly unidirectional manner, transmitting input from forebrain regions to the habenula. The SM's afferents are primarily

cholinergic Cholinergic agents are compounds which mimic the action of acetylcholine and/or butyrylcholine. In general, the word " choline" describes the various quaternary ammonium salts containing the ''N'',''N'',''N''-trimethylethanolammonium cation ...

glutamatergic Glutamatergic means "related to glutamate". A glutamatergic agent (or drug) is a chemical that directly modulates the excitatory amino acid (glutamate/aspartate) system in the body or brain. Examples include excitatory amino acid receptor agonist ...

, and

GABAergic In molecular biology and physiology, something is GABAergic or GABAnergic if it pertains to or affects the neurotransmitter gamma-aminobutyric acid (GABA). For example, a synapse is GABAergic if it uses GABA as its neurotransmitter, and a GABAergic ...

. Bilateral transection of the SM in rodents causes decreases of enzymes in the habenulae, indicating functional importance there.

Clinical significance

The SM, in conjunction with the habenula, has been identified as a potential therapeutic target for

deep brain stimulation Deep brain stimulation (DBS) is a type of neurostimulation therapy in which an implantable pulse generator is stereotactic surgery, surgically implanted subcutaneous tissue, below the skin of the chest and connected by Lead (electronics), leads ...

in the treatment of intractable depression. Preliminary results suggest significant improvement with modulation of the DDCS through SM stimulation. Given the intertwined nature of the SM and habenula, it is challenging to define a function for the SM independent of the habenula.

Sources

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References

{{Authority control Epithalamus Thalamus