Figure 1.

Schematic illustration of the fMRI tasks. (a) Tracking Stop task. The interval between horizontal (go signal) and vertical arrows (stop signal) in the stop trials becomes shorter/longer in steps of 50 ms depending on each subject's performance on previous trials ensuring 50% of correctly inhibited and 50% failed stop trials for each subject. (b) Visual–spatial Switch task. Subjects have to respond according to the arrow direction in the middle of the grid and switch their response according to the horizontal dimension (indicate whether the dot is left or right of the grid) or the vertical dimension (indicate whether the dot is above or below the grid). [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]