The watermaze delayed matching-to-place (DMP) task with search preference measure and forgetting of one-trial place memory with increasing retention delay (Experiment 1, n = 20). (A) DMP protocol: On standard training days, there are four trials (T1–T4), with the escape platform moving location between days (N, N + 1); on probe days, the retention trial is run as a probe trial on trial 2 (T2) (note absence of platform). (ΔRI) Varying retention interval. (B) Zone analysis of search preference during probe trials: Eight zones (stippled small circles, 40-cm diameter) were defined within the 2-m diameter surface of the watermaze, including a “correct” zone concentric with the location of the platform (12-cm diameter) used on T1, T3, and T4 of that day. Platform locations and zones centered on an inner ring (0.8-m diameter) and outer ring (1.4-m diameter) that were concentric with the center of the pool. Two different sets of eight nonoverlapping platforms and zones were used (only one set shown; the second set was obtained by shifting the first set by 45 degrees). (C) Acquisition of the DMP task to different platform locations across days plotted in terms of latency (seconds) (D) Performance within a day (T1–T4) averaged across interprobe days and plotted in terms of latency (seconds). (E) Percentage of time spent in the correct zone on probe trials as a function of RI. Stippled horizontal line indicates chance value for percentage time in correct zone. (F) Probe day latencies for T1–T4 with filled circles representing probe trial crossing latencies (T2). Means ± 1 SEM.
