Abstract
GOAL: Tracking moving objects with smooth pursuit eye movements is essential for many everyday tasks. These continuous, slow eye rotations critically support vision by centering and stabilizing moving images on the fovea; they prevent motion blur and enhance visual acuity. We recently discovered a strong perceptual benefit during pursuit eye movements in a trajectory prediction task [Spering et al., J. Neurophysiol., 2011]. Here we investigate the ability to predict motion trajectories in patients with schizophrenia. Previous studies with these patients have established pronounced motion perception deficits and abnormalities in pursuit, most notably, in the velocity gain. METHOD: Observers (11 patients, 12 age-matched controls) judged whether a linearly moving target ("ball") would hit/miss a stationary vertical line segment ("goal"). Ball and goal were shown briefly (200 or 500ms) on a computer monitor and disappeared before the perceptual judgment was prompted. We manipulated eye movements: observers had to track the ball with their eyes (50% trials) or fixate on the goal while the ball was moving towards fixation. RESULTS: We found similarities in pursuit eye movement accuracy (i.e., velocity gain, direction error) between patients and controls. Moreover, both groups equally showed more accurate pursuit in trials with longer presentation duration. In contrast, perceptual motion prediction performance differed between groups: Across conditions, motion prediction was overall significantly better in controls than in patients (75 vs. 68% correct). Motion prediction was also significantly better when stimuli were presented longer than when presented shorter – but only for controls (78 vs. 72% correct); patients showed no such effect of presentation duration. Together, these findings indicate that motion prediction deficits in schizophrenic patients are not mediated by pursuit eye movements alone, suggesting differential impairments in early visual processing for motion perception and pursuit.
Meeting abstract presented at VSS 2012