Abstract
The smooth pursuit system has the ability to perform predictive feedforward control of eye movements. This study attempted to examine how stimulus and behavioral histories of past trials affect the control of predictive pursuit of target motion with randomized velocities. We used sequential ramp stimuli where the rightward velocity was fixed at 16 deg/s while the leftward velocity was either fixed (predictable) at one of seven velocities (4, 8, 12, 16, 20, 24, or 28 deg/s) or randomized (unpredictable). As a result, predictive pursuit responses were observed not only in the predictable condition but also in the unpredictable condition. Linear mixed-effects (LME) models showed that both stimulus and behavioral histories of the previous two or three trials influenced the predictive pursuit responses in the unpredictable condition. Intriguingly, the goodness of fit of the LME model was improved when both historical effects were fitted simultaneously rather than when each type of historical data was fitted alone. Our results suggest that predictive pursuit systems allow us to track randomized target motion using weighted averaging of the information of target velocity (stimulus) and motor output (behavior) in past time sequences.
Highlights
The smooth pursuit system has the ability to perform predictive feedforward control of eye movements
One-way repeated-measures analyses of variance (ANOVA) with the target velocity in the left direction as the independent variable showed that all of the eye deceleration onset, the timing of eye reversal, and the mean eye deceleration varied according to the target velocity
The within-subjects correlation coefficient, which is a method used to focus on the changes in variables within each observer[28], showed that the timing of eye reversal was closely associated with the target velocity (r = − 0.90, p = 5.30 × 1 0–28) compared to eye deceleration onset (r = − 0.66, p = 2.43 × 1 0–10) and mean eye deceleration (r = − 0.43, p = 1.35 × 1 0–4)
Summary
The smooth pursuit system has the ability to perform predictive feedforward control of eye movements. When the timing of onset/offset or directional changes of the target motion is predictable, preceding eye velocity is generated according to future visual m otion[6,7] Such predictive pursuit responses are thought to be p reprogrammed[8,9], and their timing and scale can be built up with repeated trials[8,10,11]. For predictive pursuit of randomly timed stimuli, a model of ocular pursuit described by previous studies has proposed that a continual estimation of the timing of onset of future target motion is constructed by weighted averaging of stimulus history and retained in working memory so that predictive pursuit can be initiated[6,16]. This study was designed to clarify, quantitatively, the influence of both stimulus and behavioral histories on the predictive pursuit of visual motion with randomized velocity
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