Figure 1
From: A dichoptic feedback-based oculomotor training method to manipulate interocular alignment
Illustration of the training procedure with dichoptic feedback. (A) Stereoscopic shutter glasses were used to control the presentation of different images to the two eyes while eye alignment was manipulated in Experiments 1–3 (from left to right): bifoveal fixation, convergence, and divergence. The non-dominant and dominant eyes are shown in black and red (left and right eyes, respectively). In the bifoveal fixation experiment, observers were instructed to maintain fixation centrally with both eyes. In the other two experiments, observers maintained fixation with the dominant eye on the target, while shifting the gaze direction of the nondominant eye either nasally (Exp 2: convergence) or temporally (Exp 3: divergence). A stationary target dot was shown only to the dominant eye (shown in red), and gaze-contingent feedback was provided by expanding/contracting rings shown independently to the two eyes (red and black). The observer’s task was to move their eyes so that the rings were centered on the target dot. The fixation location of the nondominant eye at two different time points (time1 and time2) is indicated by F1 and F2 (not visible to subjects). At time 1, the eyes are aligned, and at time 2, the observer has completed an asymmetric vergence movement (Experiments 2 and 3), to move the gaze-contingent ring over the stationary target. In Experiments 2 and 3, a constant horizontal offset (5° in Experiment 2 and 3° in Experiment 2) was added to the ring in the non-dominant eye, such that the rings would be centered on the target when the correct gaze positions were held. Each ring decreased in size when it overlapped with the target dot, and increased when it was outside the target dot. The procedure for each trial of the Ocular Alignment task is shown in (B), using an example from Experiment 3. The ring and dot in the dominant eye were displayed in white to observers (shown in red here for visibility). Observers were instructed to center the two rings over the dot and hold this posture for 1000 ms. Immediately afterward, sensory eye dominance was measured with a pair of dichoptic Gabors with variable contrast (see “Methods”) and different orientations (− 45° and + 45°). Observers then reported the orientation of the dominant percept with a key press.
