Fig. 2.

A simplified schematic version of some of the known neural vestibulo-ocular projections responsible for the asymmetric oVEMP response to Fz BCV after unilateral vestibular loss. It is based on known anatomical projections and physiological results from Suzuki et al. ¹³ and Uchino et al. ¹⁹ that high frequency electrical stimulation of the utricular nerve results in activation of the contralateral inferior oblique muscle, and the ipsilateral superior oblique muscle via some of the pathways shown schematically here. Afferents from the saccular and utricular macula project to the vestibular nuclei, but the exact termination of these afferents is not yet known so this figure represents the present uncertainty about the exact neural connections of these afferents within the vestibular nuclei ¹⁹ as an open box. The otolithic projections to other eye muscles are not shown. Fz stimulation is indicated schematically. The afferents from the saccular macula course predominantly in the inferior vestibular nerve, and synapse on inhibitory neurons in the vestibular nucleus (black hexagon), which, in turn, project to spinal motoneurons controlling the sternocleidomastoid muscle (SCM). So the cVEMP indicates predominantly sacculo-collic function.