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Rakesh Nanjappa, Reza Azadi, Robert McPeek; Contextual saccade adaptation as a tool to investigate sequential saccades.. Journal of Vision 2016;16(12):848. doi: 10.1167/16.12.848.
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© ARVO (1962-2015); The Authors (2016-present)
Saccade adaptation can be contextual; meaning that saccade gain for the same retinotopic target location can differ depending on the context. In this study we used reflexive and sequential scanning saccades as contexts in order to investigate whether saccadic sequences are processed differently from single saccades. In Experiment 1, subjects were instructed to perform either a single downward-vertical saccade when the initial fixation point was presented at the center of the monitor (reflexive trials), or a sequence of two saccades when the fixation point was located on the right side of the monitor (scanning trials), where the second saccade of the scanning trials was the same as the saccades in the reflexive trials. The scanning and reflexive trials were interleaved. After a baseline phase, in the adapting phase, we induced opposite saccadic adaptation (gain-increasing and gain-decreasing) in the reflexive and scanning trials using a double-step procedure. The experiment terminated with a post-adapting phase, similar to the baseline. Results showed a gradual saccadic gain change, in opposite directions, for scanning and reflexive trials. The reflexive and scanning saccadic amplitudes at the end of the adapting phase and even in the post-adapting phase were significantly different, indicating strong contextual saccade adaptation. Experiment 2 was similar to Experiment 1, except that we replaced the reflexive trials with sequential saccades from the left-side of the monitor and tried to induce contextual saccade adaptation in the second saccade of the two different saccade sequences. Surprisingly, we did not find any significant shifts in saccadic gain in Experiment 2. The fact that saccades in the reflexive and scanning contexts can be adapted independently provides evidence that these two types of saccades are planned and performed differently. However scanning saccades from two different sequences cannot be adapted in opposite directions, suggesting that adaptation is transferred between them.
Meeting abstract presented at VSS 2016
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