Fig. 1.

Schematic diagram of the center-out reaching task used in the present study. A: trial sequence as presented on the visual display. White dot, center hold position; blue dot, hand position; red dot, target position. B: trial timing. The center-hold PREMOVE epoch lasts 1–2 s, followed by the MOVE epoch, which is initiated by target illumination. After holding at the target for 525 ms, the target turns green and a reward is delivered. The target then disappears, followed immediately by reappearance of the central cue (white dot) to begin the next trial. Target On times are shown by the red line, Central Cue On times by the black line, and Reward On times by the dashed line. This figure shows the task completed by monkeys A and P; the task completed by monkey L had slight differences (see materials and methods).