a small group of preganglionic parasympathetic motor neurons in the midline near the rostral pole of the oculomotor nucleus of the midbrain; the axons of these motor neurons leave the brain with the oculomotor nerve and synapse on the cells of the ciliary ganglion, which in turn innervate the sphincter muscle of the pupil and ciliary muscle. Destruction of this nucleus or its efferent fibers causes maximal paralytic dilation of the pupil; also demonstrated to project fibers to lower levels of the brainstem and all spinal levels. SYN: visceral nuclei of oculomotor nerve [TA].
