Figure 1.

Experimental design. From top to bottom, a schematic depiction of the experimental design is shown. The study was composed of 6 functional runs, each lasting 4 m 47 s (top). The first run, in yellow, is enlarged below, to highlight its structure. Every run included 2 blocked repetitions of each task (27 s) in a pseudo-random order, separated by a rest period (fixation of a white cross; 16 s) (middle; the 3 tasks are depicted in blue, red and green colors). The colored lines link highlighted tasks with a graphical description of the sequence of stimuli in each of them (bottom). Each sequence included 9 letters, 3 of which (33%, indicated by an asterisk at the right of the corresponding panel) were “targets.” As shown in the inferior-most part of the figure, each letter within the sequence was shown for 0.5 s, and was separated by the onset of the next one by a black screen lasting 2.5 s.