Edinger Westphal Nuclei EW

The Edinger-Westphal nuclei are located just dorsal to the third cranial nerve motoneurons and represent the visceral (parasympathetic portion) component of the oculomotor complex. The Edinger-Westphal nuclei provide preganglionic input to the ciliary ganglion mediating the pupillary light reflex and accommodation responses of the lens (i.e., the ciliary body). The nucleus of Perlia (located between the somatic nuclei of the primate) may also provide direct input into the iris and ciliary body, which bypasses the ciliary ganglion altogether. The primary input to the Edinger-West-phal nuclei is from the pretectal olivary nuclei, which receive direct crossed retinal input. Early physiologic and anatomic evidence supported direct ipsilateral and contralateral projections from the pretectal olivary nuclei to the Edinger-Westphal nucleus. Recent anatomic studies (injections of the retrograde tracer WGA-HRP into the Edinger-Westphal nuclei) have confirmed that there are no reciprocal connections between the olivary pretectal nuclei on opposite sides ofthe brain stem. Instead, each pretectal nucleus sends both contralateral and ipsilateral projections to each Edinger-Westphal nucleus. In addition, the Edinger-Westphal nuclei receive projections from the suprao-culomotor region of the midbrain as well as from the fastigial nuclei of the cerebellum. Most neurons in the Edinger-Westphal nuclei also respond during changes in accommodation (see later discussion) used to view a near target.

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