Which structure contains the parasympathetic cell bodies that mediate the near response via CN III to the ciliary ganglion?

• A. Pretectal area
• B. Lateral geniculate nucleus
• C. Edinger-Westphal nucleus
• D. Superior colliculus

Answer: (C)

The near response is driven by parasympathetic output from the Edinger-Westphal nucleus. These preganglionic parasympathetic cell bodies send fibers with the oculomotor nerve to the ciliary ganglion, where they synapse. Postganglionic fibers then reach the ciliary muscle to tighten the lens for near focus and the sphincter pupillae to constrict the pupil. The pretectal area handles the pupillary light reflex pathway (it relays to the Edinger-Westphal nucleus but is not the site of these parasympathetic cell bodies), the lateral geniculate nucleus is a visual-thalamic relay to cortex, and the superior colliculus mainly coordinates eye movements.