Delayed spatial match-to-sample task. a, Timing of trial events: fixation (FIX) (100 msec), cue presentation (CUE) (100 msec), delay [fixation (FIX) (250 msec), eccentric/central fixation (ECC FIX) (1500 msec), and refixation (RE-FIX) (500 msec)], and choice saccade (SACC) (500 msec). b, Schematic of visual display during task. Black squares indicate fixation target (thin lines are for illustration only; they were not visible on display) or choice targets. White square indicates cue. Arrow indicates choice saccade. Target and Distractor are the two identical choice stimuli that appeared simultaneously near the end of the trial. On/off indicate the visibility of the stimulus. E_H and E_V are horizontal and vertical eye position, respectively. The horizontal black bar groups the panels that belong to the delay period.