Figure 1.

Standard delay tasks for monkeys performed on computer-controlled push-button panel. (A) Delayed response. The subject is required to memorize the location of the illuminated button and press it after the delay period when both buttons are illuminated. (B) Delayed alternation. The subject is required to alternate pressing the left and right buttons with intervening delays. The subject’s action in the previous trial serves as a cue in the present trial. (C) Delayed match-to-sample. The subject is required to memorize the color of the light illuminated at the cue period, and after the delay, press a button illuminated with the same color. (D) Delayed object alternation. The subject is required to alternate the choice between two colors with intervening delays. In (C,D) the color with which the two buttons are illuminated at the response period is randomized between trials. Arrows indicate the button pressed by the monkey.