Ocular motor deficits in XXXX . III. Coordination of eye and @entity910 .

@entity1 @entity910 @entity191 @entity854 @entity1319
Eye-head coordination was measured in @entity1 with @entity191 as they made horizontal gaze shifts in response to predictable and unpredictable target steps and to targets moving smoothly with either constant or sinusoidally varying velocity. @entity1 preferred not to move their heads for both large and small amplitude gaze shifts. Both eye and head movement reaction times were prolonged. Saccades were hypometric and, frequently, slow. @entity910 were also slow, hypometric, and varied in amplitude for target shifts of a given amplitude. @entity1319 ( @entity1319 ) that normally stabilize gaze direction during head movement varied in gain from zero to greater than unity, and often drove the eyes off target. @entity854 occurred most commonly in @entity1 with abnormal vestibulo-ocular reflex (VOR) gain in darkness. We attribute these abnormalities of programming combined eye-head saccades to dysfunction of striatonigralcollicular circuits. Smooth gaze pursuit gain, the ratio of gaze velocity to target velocity, was lowered in @entity1 while tracking sinusoidal targets at 0.3, 0.5 and 1.0 Hz. Some @entity1 could track these targets with the head fixed but not with the head free. We attribute this to abnormal suppression of the vestibuloocular reflex. The results indicate that @entity191 impairs motor programming of coordinated eye-head gaze saccades and disrupts normal interaction between head movement and the VOR.
