Descending Fibers
The descending portion of the DLF originates in the hypothalamus. These fibers then descend through the brain 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.
Hypothalamic efferents in DLF arise from the paraventricular nucleus, supraoptic nucleus and periventricular nucleus, and send information to multiple areas, including:
- 1) midbrain central gray for pain modulation,
- 2) the medullary autonomic centers for heart rate, blood pressure, and respiration,
- 3) the ventral tegmental area,
- 4) brainstem parasympathetic nuclei (dorsal motor nucleus of the Vagus and salivatory nuclei for the eyes),
- 5) thoraco-lumbar preganglionic sympathetic neurons, and
- 6) lumbo-sacral preganglionic parasympathetic neurons.
Note that at least some of the output from the hypothalamus lies outside of the DLF, within a set of Descending Hypothalamic Fibers running next to the spinothalamic tract; lesions of this area canonically lead to ipsilateral Horner's syndrome.
Read more about this topic: Dorsal Longitudinal Fasciculus
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