Figure 1.

(A) Schematic overview of the spatial attention paradigm (not to scale). On each trial, participants were presented with a cue, and after a variable interval, with a target. In the neutral condition, the cue contained no information about the location of the target, while in the attention condition, the cue indicated whether the target would appear in the lower left or lower right quadrant of the screen on one of two fixed locations. Participants were instructed to indicate with a button response if the target was a plus sign, or a rotated plus sign. After a response was made feedback was presented and the next cue was presented 1500 ms after the onset of the last target. (B) The experimental design consisted of alternating blocks of sham (sham) and real stimulation (stim) with a 30-min break halfway through the experiment. (The sham group received sham stimulation on every block.) Horizontal lines indicate which blocks were included for the behavioral and electroencephalography (EEG) analysis. (C) F4 and P4 were stimulated in-phase at each person’s individual alpha frequency (IAF). C2, C4 and C6 were used as return electrodes and oscillated out-of-phase with F4 and P4.