Two Distinct Visual Motion Mechanisms for Smooth Pursuit: Evidence from Individual Differences (original) (raw)
Smooth pursuit eye velocity to a moving target is more accurate after an initial catch-up saccade than before, an enhancement that is poorly understood. We present a novel individual differences based method for identifying mechanisms underlying a physiological response, and use it to test whether visual motion signals driving pursuit differ pre-and postsaccade. Correlating moment-to-moment measurements of pursuit over time with two psychophysical measures of speed estimation during fixation, we find two independent associations across individuals. Presaccadic pursuit acceleration is predicted by the precision of low level (motion energy based) speed estimation, and postsaccadic pursuit precision is predicted by the precision of high level (position tracking) speed estimation. These results suggest both that a low level motion signal may drive presaccadic acceleration, and that an independent high level motion signal may drive postsaccadic precision.
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