Subnuclei of the oculomotor complex

(SR) Paired subnuclei of the superior recti, which are activated here. Note that the axons originating in the superior rectus subnuclei decussate and travel through the contralateral paired subnucleus before innervating the contralateral superior rectus muscle. (IR) Paired subnuclei of the inferior recti. (IO) Paired subnuclei of the inferior obliques. (EW) The Edinger-Westphal subnuclei, lying at the rostral end of the third nerve nuclear complex, govern parasympathetic innervation to the iris sphincter and ciliary muscle. (CCN) The central caudal subnucleus, lying at the caudal end of the third nerve nuclear complex, governs lid elevation through innervation of the levator palpebrae superioris. Neurons controlling the right and left lid are both present on either side so that a unilateral oculomotor nucleus lesion will cause bilateral ptosis. (Contributed by Dr. Marc J Dinkin.)