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. 2022 Mar 1;8(3):e09036. doi: 10.1016/j.heliyon.2022.e09036

Figure 2.

Figure 2

Behavioral task. a) Experimental design. We asked participants to judge the duration of a novel test stimulus (a horizontal or vertical grid) in comparison with the most recently presented reference stimulus (a grid with the opposite orientation). Participants fixed at one of the four corners relative to these stimuli. Three stimulus tasks (saccade, and two fixation controls) were presented in separate blocks, counterbalanced across participants. In each block, a series of 1–3 (randomized) 200ms reference stimuli were presented at centre, followed by the test stimulus (140, 170, 230 or 260ms, randomized) at the same or 90 deg rotated orientation. After each trial, participants judged whether the test stimulus duration was shorter or longer than the reference stimulus. Participants always began fixating 8.3° diagonally from one of the four corners of the reference stimulus location. In the Saccade Task, the fixation point shifted up or down to the opposite corner on the same horizontal side, 100ms before test presentation, eliciting a 25° vertical saccade during display of the test stimulus (and causing the retinal location of the stimuli to shift). The Fixation Task was performed with fixed gaze and stimuli locations whereas gaze was fixed in the Retina-Matched Fixation Task, but the location of the test stimulus was shifted to match the retinal locations of the Saccade Task. b) Temporal evaluation and eye position in the Saccade Task. After presentation of the last reference stimulus (200ms), the location of fixation point was changed. Then, the test stimulus was presented (after 100ms) and eye poison was changed (after saccade latency). Presentation of the test stimulus (with variable durations) occurred during the perisaccadic interval. c) Separate trials were used to study the time distortion effects of saccades (S), repetition (R) and both saccades and repetition (SR). Control trials without saccades and repetition were used to calculate individual time performances (ITPs) (see details in section 2.6.1). Statistical analysis and modeling processes have been performed using this arrangement of trials.