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Mark Harwood, Afsheen Khan, Annabelle Blangero; Spatial scale strongly modulates saccade adaptation.. Journal of Vision 2014;14(10):742. doi: 10.1167/14.10.742.
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© ARVO (1962-2015); The Authors (2016-present)
Introduction: Saccade experiments have predominantly used small, precise targets, despite our everyday viewing consisting of saccades between much more spatially extended objects. Recently spatial scale has been found to strongly affect saccade decisions ('Size-Latency Effect'), with larger targets invoking weaker decision signals, but little is still known about possible effects of scale on saccade adaptation. We hypothesized that the spatial spread of larger targets may increase uncertainty in error signals from large targets, leading to reduced adaptation. Methods: In three experiments we tested the effect of target size on the adaptive efficacy of intra-saccadic target steps. Experiment 1 used different diameter rings. In Experiments 2 and 3, subjects were required to bisect equal-length line pairs, at different separations. Experiment 3 varied the size of the intra-saccadic step from trial-to-trial in a sine wave pattern. Results: Contrary to our initial hypothesis, we found that larger targets (or larger target separations) produced significantly, and proportionally, larger adaptation. Larger targets were shown to have longer corrective saccade latencies due to the Size-Latency Effect. We found a positive relationship between corrective saccade latency and magnitude of adaptation. Discussion: Larger targets cause larger saccade adaptation. We argue that the increased time to make corrective saccades in these larger targets gives a greater urgency to adapt errors via the primary saccade. This suggests a new, more complex error signal for saccade adaptation, and underlines the importance of examining spatial scale during active vision processes.
Meeting abstract presented at VSS 2014
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