Vestibular influence on the binocular control of vertical-torsional nystagmus after lesions in the interstitial nucleus of Cajal

The interstitial nucleus of Cajal (iC) is a center of the velocity-to-posit ion integration for vertical and torsional eye movements. In addition, iC h as projections to and from the vestibular nuclei. Therefore the vestibular influence on the binocular alignment of vertical-torsional nystagmus after unilateral reversible iC inactivations was investigated in the alert monkey using 3D binocular search-coil recordings. The nystagmus was compared with the eye muscle rotation axes, which were corrected for the tonic ocular to rsion elicited by the iC inactivation. Rotation axes of nystagmus were diff erent for both eyes and revealed a co-activation of eye muscles similar to the effects of electrical stimulation of the anterior canal nerve. This sug gests that, in addition to the deficient neural integrator, a vestibular im balance contributes to the vertical-torsional nystagmus after iC inactivati ons. NeuroReport 11:779-784 (C) 2000 Lippincott Williams & Wilkins.