Section through superior colliculus (unlabeled) showing path of oculomotor nerve. ("Edinger-Westphal nucleus" is not on diagram, but would be near oculomotor nuclei.)
Figure showing the different groups of cells, which constitute, according to Perlia, the nucleus of origin of the oculomotor nerve.
1. Posterior dorsal nucleus.
1'. Posterior ventral nucleus.
2. Anterior dorsal nucleus.
2'. Anterior ventral nucleus.
3. Central nucleus.
4. Nucleus of Edinger and Westphal.
5. Antero-internal nucleus.
6. Antero-external nucleus.
8. Crossed fibers.
9. Trochlear nerve, with 9', its nucleus of origin, and 9", its decussation.
10. Third ventricle.
M, M. Median line.
|Parts||Provides input to Parasympathetic root of ciliary ganglion|
|Latin||nuclei accessorii nervi oculomotorii|
|Anatomical terms of neuroanatomy|
Alternatively, the Edinger-Westphal nucleus is a term often used to refer to the adjacent population of non-preganglionic neurons that do not project to the ciliary ganglion, but rather project to the spinal cord, dorsal raphe nucleus, lateral septal nuclei,lateral hypothalamic area and the central nucleus of the amygdala, among other regions 
Unlike the classical preganglionic neurons, that contain choline acetyltransferase, neurons of the non-preganglionic Edinger-Westphal nucleus contain various neuropeptides, such as Urocortin and cocaine- and amphetamine-regulated transcript.
Previously, it had been proposed to rename this group of non-preganglionic, neuropeptide-containing neurons to perioculomotor subgriseal neuronal stream, abbreviated pIIISG.
However, more recently, a final nomenclature has been determined. Preganglionic oculomotor neurons within the Edinger-Westphal nucleus shall be referred to as the EWpg, and the neuropeptide-containing neurons shall be known as the centrally-projecting Edinger Westphal nucleus, or EWcp.
It is the most rostral of the parasympathetic nuclei in the brain stem.
It has also been implicated in the mirroring 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.