Figure 1.

Experimental paradigm. Two vertical bars were presented, with the left and right denoting the little and index finger of the left hand or the index and little finger of the right hand. Filled pink color indicated the pressing force of the responding finger, where a completely filled pink bar indicated 50% of MVC of that finger. The warning cue was a red horizontal line at one of three locations (corresponding to 10%, 25%, and 40% of MVC) on one of the vertical bars, indicating which finger to press and the effort level required. Subjects were asked to press with the correct finger with the appropriate level of effort at the onset of the filled circle go cue and to hold the force until the circle was extinguished.