The dorsal longitudinal fasciculus (DLF) is a distinctive

nerve tract A nerve tract is a bundle of nerve fibers (axons) connecting Nucleus (neuroanatomy), nuclei of the central nervous system. In the peripheral nervous system, this is known as a nerve fascicle, and has associated nervous tissue, connective tissue. T ...

in the

midbrain The midbrain or mesencephalon is the uppermost portion of the brainstem connecting the diencephalon and cerebrum with the pons. It consists of the cerebral peduncles, tegmentum, and tectum. It is functionally associated with vision, hearing, mo ...

. It extends from the

hypothalamus The hypothalamus (: hypothalami; ) is a small part of the vertebrate brain that contains a number of nucleus (neuroanatomy), nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrin ...

rostrally to the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue that extends from the medulla oblongata in the lower brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal c ...

caudally, and contains both descending and ascending fibers. Descending fibers arise in the hypothalamus to project directly or indirectly onto autonomic nuclei and

lower motor neurons Lower motor neurons (LMNs) are motor neurons located in either the anterior grey column, anterior nerve roots (spinal lower motor neurons) or the cranial nerve nuclei of the brainstem and cranial nerves with motor function (cranial nerve lower ...

of the brainstem and spinal cord; the descending component is involved in controlling chewing, swallowing, salivation and gastrointestinal secretory function, and shivering. Among the ascending fibers is a

serotonin pathway A serotonin pathway identifies aggregate projections from neurons which synthesize and communicate the monoamine neurotransmitter serotonin. These pathways are relevant to different psychiatric and neurological disorders. Pathways Function Gi ...

arising in the

raphe nuclei The raphe nuclei (, "seam") are a moderate-size cluster of nuclei found in the brain stem. They have 5-HT1 receptors which are coupled with Gi/Go-protein-inhibiting adenyl cyclase. They function as autoreceptors in the brain and decrease the ...

Anatomy

Ascending fibers

Fibres arising from the nuclei of the

reticular formation The reticular formation is a set of interconnected nuclei in the brainstem that spans from the lower end of the medulla oblongata to the upper end of the midbrain. The neurons of the reticular formation make up a complex set of neural networks ...

ascend in the DLF to terminate in the

. It conveys

visceral In a multicellular organism, an organ is a collection of Tissue (biology), tissues joined in a structural unit to serve a common function. In the biological organization, hierarchy of life, an organ lies between Tissue (biology), tissue and an o ...

information to the

brain The brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for ...

. Fibers arising from the parabrachial area pass in the DLF to convey taste and general visceral sensation from the nucleus tractus solitarii to the posterior nucleus and periventricular nuclei of the hypothalamus. A small ascending dorsal serotonergic pathway arising from the ventral and dorsal superior

initially travels in the DLF, with some of its fibres terminating in the

periaqueductal gray The periaqueductal gray (PAG), also known as the central gray, is a brain region that plays a critical role in autonomic function, motivated behavior and behavioural responses to threatening stimuli. PAG is also the primary control center for ...

of the midbrain, and the posterior hypothalamus; the majority of its fibers however pass beyond the DLF in the medial forebrain bundle, here uniting with fibres of the more substantial ventral serotonergic pathway to commonly terminate diffusely across structures of the

forebrain In the anatomy of the brain of vertebrates, the forebrain or prosencephalon is the rostral (forward-most) portion of the brain. The forebrain controls body temperature, reproductive functions, eating, sleeping, and the display of emotions. Ve ...

Descending fibers

The descending fibers of the DLF commence in the medial zone of the hypothalamus as largely unmyelinated axons having originated from the

paraventricular nucleus of hypothalamus The paraventricular nucleus (PVN) is a nucleus in the hypothalamus, located next to the third ventricle. Many of its neurons project to the posterior pituitary where they secrete oxytocin, and a smaller amount of vasopressin. Other secretion ...

. The axons converge to form a distinct bundle in the

of the

. Still more caudally, the DLF passes in the medial portion of the floor of the fourth ventricle. Descending fibers of the DLF may first synapse in either the periaqueductal gray or reticular formation which in turn form relay projections onto the autonomic nuclei of the brainstem, and the lower motor neurons of the brainstem and spinal cord, respectively. Some fibers project directly to the dorsal nucleus of vagus nerve, and autonomic nuclei of the spinal cord (hypothalamospinal fibers). Descending projections of the DLF are functionally involved in mediating chewing, swallowing, salivation and gastrointestinal secretory function, and shivering. * Medial zone of

→

(synapse) → solitary nucleus, dorsal nucleus of vagus nerve. *

Hypothalamus The hypothalamus (: hypothalami; ) is a small part of the vertebrate brain that contains a number of nucleus (neuroanatomy), nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrin ...

→

(synapse) → ** → reticulonuclear tract → lower motorneurons of the brainstem. ** → reticulospinal tract →

lower motor neuron Lower motor neurons (LMNs) are motor neurons located in either the anterior grey column, anterior nerve roots (spinal lower motor neurons) or the cranial nerve nuclei of the brainstem and cranial nerves with motor function (cranial nerve lower ...

of the spinal cord. * Medial habenular nucleus → fasciculus retroflexus → interpeduncular nucleus of midbrain → midbrain

→ dorsal longitudinal fasciculus → autonomic pre-ganglionic neurons. This pathway is involved in the autonomic regulation of mastication (chewing), deglutition (swallowing), and salivary and gastrointestinal secretory function. The salivatory nuclei receive hypothalamic afferents which perhaps pass through the DLF.

References

External links

NIF Search - Dorsal longitudinal fasciculus
via the

Neuroscience Information Framework The Neuroscience Information Framework is a repository of global neuroscience web resources, including experimental, clinical, and translational neuroscience databases, knowledge bases, atlases, and genetic/ genomic resources and provides many aut ...

{{Authority control Hypothalamus Brainstem