Figure 1.

Serial probe recognition task and behavioral performance of monkeys. A, Trial structure for the serial probe recognition task. The monkey pulled the joystick to initiate each trial (Warning). Four cue items (i.e., objects) to study were then presented sequentially (Initial, Middle, and Last items). After a 7–10 s delay (Delay), two choice symbols were presented along with a test item (Choice). The symbols, a triangle and a cross, were differentially defined as “seen” and “unseen” for each monkey (see inset table). Monkeys were required to select the “seen” (or “unseen”) symbol if the test item was (or was not) included in the studied list of items. The classification of the Hit and CR trials for Monkey A is shown here. B, The percentage of correct (filled bars) and incorrect (open bars) responses made by each monkey when the test item was the first object presented in the list (Initial) or the second or third items presented in the list (Middle) in the serial probe recognition task during the scanning sessions. *p < 0.05 (χ² test).