Experimental paradigm.

<p>Schema of the training (A) and fMRI (B) sessions. A) During the training session, the following visual stimuli were sequentially presented at the center of the screen: a white cross (1.5 s), a green cross persisting until the central button was pressed, an arrow facing left or right (signaling whether the left or right button had to be pressed to stop the time interval), and a visual/acoustic feedback (500 ms) about the accuracy of the produced interval. B) During the fMRI session, the same sequence was adopted, but with male or female (painful or neutral) faces instead of arrows. During both sessions, production of a 3 s time interval was requested during each trial. No feedback was given on the accuracy of the time intervals during the fMRI experiment.