Abstract
Errors in eye movements can be corrected during the ongoing saccade through in-flight modifications (i.e., online control), or by programming a secondary eye movement (i.e., offline control). In a reflexive saccade task, the oculomotor system can use extraretinal information (i.e., efference copy) online to correct errors in the primary saccade, and offline retinal information to generate a secondary corrective saccade. The purpose of this study was to examine the error correction mechanisms in the antisaccade task. The roles of extraretinal and retinal feedback in maintaining eye movement accuracy were investigated by presenting visual feedback at the spatial goal of the antisaccade. We found that online control for antisaccade is not affected by the presence of visual feedback; that is whether visual feedback is present or not, the duration of the deceleration interval was extended and significantly correlated with reduced antisaccade endpoint error. We postulate that the extended duration of deceleration is a feature of online control during volitional saccades to improve their endpoint accuracy. We found that secondary saccades were generated more frequently in the antisaccade task compared to the reflexive saccade task. Furthermore, we found evidence for a greater contribution from extraretinal sources of feedback in programming the secondary “corrective” saccades in the antisaccade task. Nonetheless, secondary saccades were more corrective for the remaining antisaccade amplitude error in the presence of visual feedback of the target. Taken together, our results reveal a distinctive online error control strategy through an extension of the deceleration interval in the antisaccade task. Target feedback does not improve online control, rather it improves the accuracy of secondary saccades in the antisaccade task.
Highlights
Saccades are stereotypical eye movements characterized by the main sequence, which describes the linear relationship between saccade amplitude and peak velocity/duration [1]
In the case of antisaccades, we found that: (1) the extension of antisaccade deceleration interval is a feature of online control that was associated with improved accuracy; (2) target feedback presented at the spatial goal of the antisaccade does not alter the dynamics of the ongoing eye movement; (3) generation of secondary saccades is an important control strategy that improves endpoint accuracy of antisaccades, which is further enhanced by, visual feedback
Online control of antisaccades In agreement with previous studies, we found that antisaccades had longer latency, lower accuracy and greater variability compared to reflexive saccades [3,8,22,35,36,37]
Summary
Saccades are stereotypical eye movements characterized by the main sequence, which describes the linear relationship between saccade amplitude and peak velocity/duration [1]. We investigated the error correction processes in antisaccades, which are volitional eye movements that require suppression of a reflexive saccade towards a visual target, and generation of a saccade towards a location that is the mirror opposite of where the target was presented [3]. The successful execution of the antisaccade requires two higher cognitive processes: inhibition of a reflexive saccade and inversion of the saccade vector in order to make an eye movement to the mirror location. Saccade accuracy can be maintained via two control mechanisms: online (i.e., in-flight corrections during the ongoing primary saccade) and offline (i.e., programming of a secondary eye movement) Details of these two error correction mechanisms are discussed below
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