Figure 1.

Experimental design. A graphic representation of the six stimulation sites was shown before stimulus application. Fully approved sites were shown in a different color than sites approved with reservations. The site stimulated in the current trial was highlighted by a gray square. Subsequently, the laser stimulus calibrated to pain-threshold intensity was applied to the right foot. Participants were then prompted to indicate by a button press (here, left button for “yes” = pain and right button for “no” = no pain) whether the stimulus had been perceived as painful or not. Assignment of buttons was varied from trial to trial. Following the button press, the presentation of a fixation cross ended the trial.