Fig. 1.

A: positions of the fixation point (FP) and the saccade target (T1) for the adaptation procedure. During execution of the saccade, the saccade target jumped in the outward direction. B: time course of events for the adaptation procedure. While subjects kept their gaze on the fixation point, saccade target T1 appeared. When the fixation point disappeared, subjects had to perform a saccade to T1. With this method, 3 different overlap durations (indicated by the gray vertical bar) of fixation point and saccade target (0, 250, 500 ms) could be tested. When the eye tracker detected the change in the horizontal eye position (H EP), the saccade target was displaced. C: positions of the fixation point and the saccade target (T1) in the “combined condition” were the same as in the adaptation procedure. D: time course of events in the combined condition. Subjects performed a saccade to the position of the saccade target when the fixation point disappeared. The saccade target was shown for either 50 or 500 ms together with the fixation point. E: positions of the fixation point and the saccade targets (T1 and T2) in the “spatiotopic condition.” Subjects fixated on the fixation point until saccade target T1 appeared and then performed a saccade to T1. From T1 they had to initiate a saccade to T2. F: time course of events in the spatiotopic condition. The gray vertical bar indicates the overlap period of saccade targets T1 and T2 (which could be either 50 or 500 ms). When T1 disappeared, subjects had to saccade to the position of T2. V EP, vertical eye position.