Simulation of pathological ocular counter-roll and skew-torsion by a 3-D mathematical model

A basic version of a 3-D mathematical model for simulation of otolithic con trol of binocular static eye position was extended by introducting excitato ry commissural fibers between the vestibular nuclei, and physiological non- linearities: the force-response relationship of utricular neurons and a qua dratic relationship between eye muscle innervation and force. These modific ations appeared to be necessary in order to simulate the gain asymmetry of ocular counter-roll to lateral head tilt in patients with unilateral utricu lar loss. The current model can adequately simulate skew-torsion in patient s with unilateral utricular loss, lesions of the vestibular nuclei, and cen tral graviceptive pathway lesions. The direction of simulated skew-torsion corresponds satisfactorily to data from normals and patients with acute ves tibular loss. The relatively low values of predicted eye deviations for per ipheral vestibular lesions suggest that part of the effects seen in patient s is caused by affection of the semicircular canals. NeuroReport 10:1843-18 48 (C) 1899 Lippincott Williams & Wilkins.