Dorsal longitudinal fasciculus

The dorsal longitudinal fasciculus (DLF) (not to be confused with the medial longitudinal fasciculus) is a white matter fiber tract located within the brain stem, specifically in the mesencephalon. The DLF travels through the periaqueductal gray matter.

As with all white matter tracts, the DLF consists of myelinated axons carrying information between neurons. The DLF carries both ascending and descending fibers.

Ascending fibers
The DLF ascending tract has its origins in nuclei of the reticular formation. These fibers synapse onto the hypothalamus and carry visceral information to the brain.

Descending fibers
The descending portion of the DLF originates in the hypothalamus. These fibers then descend through the brian stem periaqueductal gray matter along the base of the fourth ventricle. These fibers continue on into the spinal cord where they synapse with preganglionic autonomic neurons.