Fig. 1.

Appearance of the computer monitor during the different events of the WCST task. WCST trials are shown on theleft, control trials on the right. Thetop four cards (on the monitor) are the reference cards, and the bottom card is the test card. During the matching period, the subject chooses the reference card that matches the test card by moving the orange cursor beneath the cards using computer mouse buttons. In the WCST trials, a change in screen brightness during the feedback period indicates a correct or incorrect match. The four subtractions used for data analysis are also illustrated. A, Event 1 minus control event 5;B, event 2 minus control event 6;C, event 3 minus control event 5; D, event 4 minus control event 6 (see Materials and Methods).