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Rakesh Nanjappa, Robert McPeek; Microsaccades while aiming are not just limited by gaze relocation demands.. Journal of Vision 2017;17(10):886. doi: https://doi.org/10.1167/17.10.886.
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Microsaccades are part of oculomotor strategy during fine acuity visuomotor tasks. For example when threading a needle, microsaccades initially relocate gaze between the distinct objects of interest to facilitate fine motor adjustments, after which their rate declines as the objects move closer. A similar trend in microsaccade rate is seen during shooting tasks even though the objects involved do not move in a predictable manner. We investigated microsaccade characteristics while subjects controlled the direction of a slow moving circle with a gamepad to make it concentric with another fixed circular target and pressed a button to trigger a 'shoot' event. In one condition, both the fixed and moving targets appeared straight ahead at one degree separation between their centers. In the second condition the targets were presented with similar separation and motion at 5 degrees eccentricity, and subjects maintained fixation on a central target and used peripheral vision to perform the task. Aiming performance was much better with the use of central vision and dropped dramatically when peripheral vision was used. Microsaccade direction was highly correlated with the moving target's position in both the conditions. There was no significant coupling between the timing of microsaccades and motor adjustments. In the central viewing condition, microsaccade rate dropped just before the shooting event, as observed in earlier studies. This drop has been associated with the narrowing separation between the two objects and the resulting lack of need for microsaccades to foveate them alternately. Surprisingly, we found a similar drop in microsaccade rate just before shooting in the peripheral viewing condition in which microsaccades do not relocate gaze between objects. This indicates that the drop in microsaccade rate is affected not only by changes in gaze relocation demands, but also by other factors, such as attention or the perceptual decision-making process.
Meeting abstract presented at VSS 2017
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