Figure 1. The trial procedure and design of the fMRI version of ANT used in the study
ANT fMRI Task
The procedure of the ANT fMRI task was thoroughly introduced in previous studies (Madhyastha et al. , 2015; Boord et al. , 2017; Dayet al. , 2019). Figure 1 illustrates the single trial procedure and task design. At the onset of each trial, a cue or a fixation appeared against a gray background for 200 milliseconds (ms), according to the trial type. For the “no cue” condition, the screen only had a fixation at the center. For the “center cue” condition, an asterisk appeared at the center of the screen to alert the target’s appearance. For the “spatial cue” condition, along with the center fixation, an asterisk appeared on the top or the bottom, indicating the possible position of the target. After a randomly jittered period, ranging from 300 ms to 11800 ms, a flanker target compositing with five arrows (each subtending 0.56° of visual angle, separated by 0.05°) appeared on the top or the bottom of fixation (1.06° apart from the center). Participants had to respond to the direction of the center arrow within a time window of 2000 ms. The direction of the center arrow could be the same as the side arrow (congruent condition) or different (incongruent condition). After response or time-out, a random inter-trial interval was followed (mean: 4000 ms, ranging from 1000 ms to 13000 ms). The cue type (no cue, center cue, spatial cue) and congruence (congruent, incongruent) factors were orthogonal, making a balanced design. There were six blocks per scanning session. Participants completed two buffered trials (discarded before analysis) and 36 reaction time trials for each block. All participants completed two scanning sessions separated by one to three weeks.