The Edinger–Westphal nucleus also called the accessory or visceral oculomotor nerve, is one of the two nuclei of the oculomotor nerve (CN III) located 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 receives afferents from both pretectal nuclei (which have in turn received afferents from the

optic tract In neuroanatomy, the optic tract () is a part of the visual system in the brain. It is a continuation of the optic nerve that relays information from the optic chiasm to the ipsilateral lateral geniculate nucleus (LGN), pretectal nuclei, and su ...

). It contains

parasympathetic The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system, the others being the sympathetic nervous system and the enteric nervous system. The autonomic nervous system is responsible for regulat ...

pre-ganglionic neuron cell bodies that synapse in the

ciliary ganglion The ciliary ganglion is a parasympathetic ganglion located just behind the eye in the posterior orbit. It is 1–2 mm in diameter and in humans contains approximately 2,500 neurons. The ganglion contains postganglionic parasympathetic neurons. T ...

. It contributes the autonomic, parasympathetic component to the oculomotor nerve (CN III), ultimately providing innervation to the

iris sphincter muscle The iris sphincter muscle (pupillary sphincter, pupillary constrictor, circular muscle of iris, circular fibers) is a muscle in the part of the eye called the iris. It encircles the pupil of the iris, appropriate to its function as a constricto ...

and

ciliary muscle The ciliary muscle is an intrinsic muscle of the eye formed as a ring of smooth muscleSchachar, Ronald A. (2012). "Anatomy and Physiology." (Chapter 4) . in the eye's middle layer, the uvea ( vascular layer). It controls accommodation for vie ...

to mediate the

pupillary light reflex The pupillary light reflex (PLR) or photopupillary reflex is a reflex that controls the diameter of the pupil, in response to the intensity ( luminance) of light that falls on the retinal ganglion cells of the retina in the back of the eye, t ...

and accommodation, respectively. The Edinger–Westphal nucleus has two parts. The first is of preganglionic fibers (EWpg) that terminate in the ciliary ganglion. The second is of centrally projecting cells (EWcp) that project to a number of

brainstem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is conti ...

structures.

Structure

The Edinger–Westphal nucleus refers to the adjacent population of non-preganglionic neurons that do not project to the

, but rather project 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 ...

dorsal raphe nucleus The dorsal raphe nucleus is one of the raphe nuclei. It is situated in the brainstem at the midline. It has rostral and caudal subdivisions: * The rostral aspect of the ''dorsal'' raphe is further divided into interfascicular, ventral, ventrolater ...

, lateral

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 hypothalamic area and the

central nucleus of the amygdala The central nucleus of the amygdala (CeA or aCeN) is a nucleus within the amygdala. It serves as the major output nucleus of the amygdala and participates in receiving and processing pain information. CeA connects with brainstem areas that cont ...

, among other regions.. Unlike the classical preganglionic neurons that contain

choline acetyltransferase Choline acetyltransferase (commonly abbreviated as ChAT, but sometimes CAT) is a transferase enzyme responsible for the synthesis of the neurotransmitter acetylcholine. ChAT catalyzes the transfer of an acetyl group from the coenzyme acetyl-Co ...

, neurons of the Edinger–Westphal nucleus contain various

neuropeptide Neuropeptides are chemical messengers made up of small chains of amino acids that are synthesized and released by neurons. Neuropeptides typically bind to G protein-coupled receptors (GPCRs) to modulate neural activity and other tissues like the ...

s such as urocortin and

cocaine- and amphetamine-regulated transcript Cocaine- and amphetamine-regulated transcript, also known as CART, is a neuropeptide protein that in humans is encoded by the ''CARTPT'' gene. CART appears to have roles in reward, feeding, and stress, and it has the functional properties of a ...

. Previously, it has been proposed to rename this group of non-preganglionic, neuropeptide-containing neurons to ''perioculomotor subgriseal neuronal stream'' (''pIII_SG''). It has also been suggested that the preganglionic oculomotor neurons within the Edinger–Westphal nucleus be referred to as the ''EWpg'', and the neuropeptide-containing neurons be known as the centrally-projecting Edinger Westphal nucleus, or ''EWcp''.

Anatomical relations

The paired nuclei are posterior to the main motor nucleus (

oculomotor nucleus The fibers of the oculomotor nerve arise from a nucleus in the midbrain, which lies in the gray substance of the floor of the cerebral aqueduct and extends in front of the aqueduct for a short distance into the floor of the third ventricle. F ...

) and anterolateral to the

cerebral aqueduct The cerebral aqueduct (aqueduct of the midbrain, aqueduct of Sylvius, Sylvian aqueduct, mesencephalic duct) is a small, narrow tube connecting the third and fourth ventricles of the brain. The cerebral aqueduct is a midline structure that passe ...

in the

rostral Rostral may refer to: Anatomy * Rostral (anatomical term), situated toward the oral or nasal region * Rostral bone, in ceratopsian dinosaurs * Rostral organ, of certain fish * Rostral scale The rostral scale, or rostral, in snakes and other sca ...

at the level of the

superior colliculus In neuroanatomy, the superior colliculus () is a structure lying on the tectum, roof of the mammalian midbrain. In non-mammalian vertebrates, the Homology (biology), homologous structure is known as the optic tectum or optic lobe. The adjective f ...

. It is the most rostral of the parasympathetic nuclei in the

brain stem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is co ...

Function

The Edinger–Westphal nucleus supplies

preganglionic In the autonomic nervous system, nerve fibers from the central nervous system to the autonomic ganglion, ganglion are known as preganglionic nerve fibers. All preganglionic fibers, whether they are in the sympathetic nervous system, sympathetic d ...

parasympathetic fibers to the

eye An eye is a sensory organ that allows an organism to perceive visual information. It detects light and converts it into electro-chemical impulses in neurons (neurones). It is part of an organism's visual system. In higher organisms, the ey ...

, constricting the pupil, accommodating the

lens A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements'') ...

, and convergence of the eyes.

Neurophysiology

Pupillary light reflex

The EWN is located in the midbrain, adjacent to the oculomotor nucleus. It consists of preganglionic parasympathetic neurons that send axons through the oculomotor nerve (CN III) to synapse in the ciliary ganglion. The postganglionic fibers from the ciliary ganglion then innervate the iris sphincter muscle, leading to pupillary constriction (miosis) in response to light. The EWN also receives modulatory feedback from the locus coeruleus (LC), a noradrenergic center in the pons. The LC integrates information about ambient illumination and cognitive states, adjusting EWN activity accordingly. This interplay allows for dynamic pupil size regulation, balancing light adaptation with cognitive demands such as attention and arousal. The role of the EWN in the pupillary light reflex is crucial for maintaining visual acuity and protecting retinal photoreceptors from excessive light exposure. Dysfunction of the EWN can lead to neurological deficits, including impaired pupillary reflexes seen in conditions such as diabetic autonomic neuropathy, oculomotor nerve palsy, and neurodegenerative disorders.

Research

It has also been implicated in the

mirroring Mirroring is the behavior in which one person subconsciously imitates the gesture, idiolect, speech pattern, or attitude of another. Mirroring often occurs in social situations, particularly in the company of close friends or family, often going ...

of pupil size in sad facial expressions. When seeing a sad face, participants' pupils dilated or constricted to mirror the face they saw, which predicted both how sad they perceived the face to be, as well as activity within this region.

Eponym

The nucleus is named for both Ludwig Edinger, from

Frankfurt Frankfurt am Main () is the most populous city in the States of Germany, German state of Hesse. Its 773,068 inhabitants as of 2022 make it the List of cities in Germany by population, fifth-most populous city in Germany. Located in the forela ...

, who demonstrated it in the

fetus A fetus or foetus (; : fetuses, foetuses, rarely feti or foeti) is the unborn offspring of a viviparous animal that develops from an embryo. Following the embryonic development, embryonic stage, the fetal stage of development takes place. Pren ...

in 1885, and for

Karl Friedrich Otto Westphal Karl Friedrich Otto Westphal (23 March 1833 – 27 January 1890) was a German psychiatrist from Berlin. He was the son of Otto Carl Friedrich Westphal (1800–1879) and Karoline Friederike Heine and the father of Alexander Karl Otto Westphal (18 ...

, from

Berlin Berlin ( ; ) is the Capital of Germany, capital and largest city of Germany, by both area and List of cities in Germany by population, population. With 3.7 million inhabitants, it has the List of cities in the European Union by population withi ...

, who demonstrated it in the

adult An adult is an animal that has reached full growth. The biological definition of the word means an animal reaching sexual maturity and thus capable of reproduction. In the human context, the term ''adult'' has meanings associated with social an ...

in 1887.

Additional images

File:Gray696.png, The cranial nerve nuclei schematically represented; dorsal view. Motor nuclei in red; sensory in blue. File:Gray697.png, Nuclei of origin of cranial motor nerves schematically represented; lateral view. File:Gray698.png, Primary terminal nuclei of the afferent (sensory) cranial nerves schematically represented; lateral view.

References

External links

Diagram at Columbia
* * * {{DEFAULTSORT:Edinger-Westphal nucleus Cranial nerve nuclei Oculomotor nerve Midbrain