Abstract
When humans pursue sinusoidal target motion they rapidly learn to track with minimal phase error despite inherent visuo-motor processing delays; prior evidence suggests that prediction might even occur within the first cycle. Here, this has been examined by evoking reactive responses to single cycle stimuli having randomised periodicity and peak velocity. Periodicity was varied within three specific ranges with differing average periodicity. Initial responses in the first half-cycle were remarkably similar within periodicity ranges, irrespective of target velocity or frequency, but differed between ranges. In contrast, in the second half-cycle eye velocity closely matched the target in velocity and timing, irrespective of differences in eye velocity in the first half. Abrupt transitions occurred between first and second half-cycles, consistent with the hypothesis that target motion information is sampled and stored within the first half-cycle, irrespective of actual eye velocity evoked, and then released as a predictive estimate in the second half.
Highlights
The majority of experiments in which the initial component of ocular pursuit has been investigated have focussed on responses to randomised presentation of ramp or step-ramp stimuli (e.g. Carl & Gellman (1987))
Within these responses it is evident that the response to the first half-cycle lags behind the stimulus and frequently has reduced peak velocity, in the second half-cycle there is much less phase error and peak eye velocity is generally closer to target velocity
The most notable feature is that, within each range, the responses in the first half-cycle are initially very similar, with eye velocity rising to a similar peak velocity at a similar time irrespective of frequency; in contrast, those in the second half-cycle match target velocity more closely, with regard to the timing of peak velocity
Summary
The majority of experiments in which the initial component of ocular pursuit has been investigated have focussed on responses to randomised presentation of ramp or step-ramp stimuli (e.g. Carl & Gellman (1987)). The majority of experiments in which the initial component of ocular pursuit has been investigated have focussed on responses to randomised presentation of ramp or step-ramp stimuli The aim of the current experiment was to examine what happens to the pursuit response in the transition between the onset of the initial visually driven component and the attainment of the predictive state. It is known from a previous experiment that this can happen very quickly (Barnes, Barnes, & Chakraborti, 2000). The objective of the current experiment was to investi-
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