Fig. 1: Methods.

A 100 % validity cued target-detection task with distractors. To initiate the trial, monkeys had to hold a bar with the hand and fixate their gaze on a central cross on the screen. Monkeys received liquid reward for releasing the bar 150−750 ms after target presentation onset. Target location was indicated by a cue (green square, second screen). Monkeys had to ignore any un-cued event (distractors). Monkeys were instructed to keep their gaze on the fixation point (white dashed lines), therefore they had to detect the stimuli using selective spatial attention (red dashed lines). B On each session, one 24-contact recording probe was placed in right FEF (top) and left FEF (bottom). C Single MUA mean ( ± s.e.) associated to when cue is orienting towards the preferred (black) or the anti-preferred (gray) spatial location, during the cue-to-target interval. D Distribution of attention modulation index (Preferred-Anti-preferred)/(Preferred + Anti-Preferred), computed over 200 ms before target onset across all MUAs of all sessions. Black histogram corresponds to channels in which the neuronal activity during this time interval was significantly different between the preferred and the anti-preferred spatial attention responses (Two-sided Wilcoxon signed-rank test, p < 0.05: black, significant difference).