Fig. 7. Unilateral loss of the utricle, causing pathologic ocular tilt reflex. A. Disruption of the left utricular division of the VIIIth nerve from vestibular neuritis. B. The pathologic ocular tilt reflex from this lesion. Relative excitation of the right medial vestibular nucleus (M) causes elevation and intorsion of the right eye (mediated by the right superior rectus and right superior oblique muscles), and causes depression and extorsion of the left eye (mediated by the left inferior rectus and left inferior oblique muscles). Excitation of the neck muscles innervated by the intact vestibulospinal tract causes a left head tilt.