Fig. 1: Concurrent TMS-fMRI task.

On each trial, participants saw a target object that they had to categorise according to either its form (angular/curvilinear) or colour (green/blue) in alternating blocks (a). A picture cue at the start of each block indicated the current task (form or colour; b). On each trial, a cue reminded participants of the current task (500 ms) followed by the object to categorise (100 ms), during which they received a train of 3 TMS pulses (13 Hz, high or low intensity, onset 75 ms after stimulus). Participants were instructed to respond before the white cross (500 ms) turned black. If participants responded within 500 ms, the white cross turned black for the remainder of the 500 ms and was in either case followed by a black cross for a jittered interval of 3500–4000 ms. In the example shown, participants are cued to attend to shape and the correct response would be the left button. The stimulus–response mappings for the two dimensions meant that for some stimuli, their shape and colour required the same button response (congruent) and for other stimuli, their shape called for one button and its colour called for the other button (incongruent). The trial depicted in this figure is a congruent trial as the correct button response for its shape is left, and its blue colour would also have indicated the left button during the colour task. In (c), the four presented objects are displayed prior to masking for illustration purposes.