Figure 1.

Performance in the DNMS task. (A) Delay-dependent DNMS performance is indicated as mean (± SEM) percent of correct trials per session (100–200 trials), averaged across 7 different animals. Trials were grouped and plotted by 5-sec intervals across the 1- to 30-sec delay intervals. Horizontal dashed lines indicate a 6% delay-dependent decrement in DNMS performance contributed by trials with delays of <15 sec (left of vertical dashed line), and an additional 14% delay-dependent decrement contributed by trials with delays ≥15 sec. (B) Effect of proactive interference on DNMS performance. The data shown in A were sorted, on the basis of preceding trial type (which was determined with respect to lever press position in the sample phase of the trial), into the Same category or the Different category. Mean (± SEM) percent of correct DNMS performance by delay is plotted separately for each of the sorted trial types. The dashed line is the overall mean DNMS performance curve from A. Proactive interference is demonstrated by the consistent 6–8% decrease in DNMS performance at each delay (relative to Same trials) for Different trials.