Figure 1.

Stimulus configuration and temporal structure of the shape-tracking task. (A) Schematic illustration of task conditions. Black arrows indicate the cued target stimulus; other stimuli serve as distractors. The RF of the recording site in V4 is depicted as a gray circle, which does not appear on the display. Trials could contain either one or two stimuli in the V4 RF. The abbreviations indicate the number of stimuli within the RF (“S” for single and “D” for double presentation in the V4 RF) and the direction of attention to either the stimulus inducing higher “⁺” or lower values “⁻” of spiking activity or γ-synchronization. The condition with two stimuli in the RF but attention directed to stimuli in the opposite hemi-field is referred to as D⁰ (Double Attend Out). (B) Temporal structure of the shape-tracking task. During the cueing period, a spatial cue was present on screen. The cue was a simple ring for monkey T and a ring enclosing the upcoming target shape for monkey B. After appearance of the fixation point (FP), monkeys started fixation and initiated the trial by pressing a lever. Simultaneously, the spatial cue disappeared (faded within 200 ms for monkey B). After a baseline period (Bas.), followed by static presentation (Stc.) of the initial shapes at each location, they morphed through a sequence of different shapes until the initial shape at the cued location reappeared. Monkeys had to signal this reappearance within a response period indicated by the dashed rectangle. Bas, baseline period; Cue, Cueing period; FP, fixation point; MC, morph cycle; Stc, static presentation period.