Article Figures & Data
Figures
- Figure 1.
Schematic of the spatial-association task. A, At the beginning of the session-1 learning phase, each object was initially presented in a unique screen location on a 1024 × 768 pixel (26.67 × 20 cm) grid, viewed from a distance of 92 cm. After all learning trials, participants completed the first cued-recall test (T1). In this test, objects were shown in the center of the screen and participants were prompted to move each object to its original location. B, At session 2, EEG was recorded while participants completed the second cued-recall test (T2). For the Active condition, participants viewed each object for 1500 ms and then were prompted to move the object to its original location. For the Covert condition, participants prepared to recall the original location as in the Active condition, and likely attempted to retrieve the location during this time, but they had no opportunity to move the object. Trials in the Active and Covert conditions were randomly intermixed. C, At session 3, participants completed the final cued-recall test (T3). D, The original location for one example object in the Active condition is labeled “Study.” Solid white lines depict the distance the object was placed from the study location at each test. Typical errors made on each of the three tests as shown: mean error of 3.59 cm at T1, mean error of 4.73 cm at T2 (Active condition only), and mean error of 5.01 cm at T3. The dashed white line depicts the distance the object was placed from the T2 retrieved location at the final test (retrieval bias distance).
- Figure 2.
Mean errors in the spatial-association task. Errors on each test (T1, T2, and T3) were computed as the distance objects were placed from corresponding study locations. At T3, forgetting across days was significantly less for objects in the Active Retrieval condition versus the No Retrieval condition. Over all three conditions, errors were greater on T3 than on T1 (t(11) = 8.77, p < 0.001). For the Active Retrieval condition, errors were greater on T2 than on T1 (t(11) = 5.07, p < 0.001) and greater on T3 than on T2 (t(11) = 2.42, p < 0.05). Error bars show SEM after removing across-subject variability.
- Figure 3.
Retrieval bias contrasted with memory accuracy for the Active condition. Locations recalled at T3 were 4.92 cm (SE = 0.06) from the study location on average (memory accuracy) and 3.59 cm (SE = 0.06) from the T2 retrieved location on average (retrieval bias). Bins correspond to the proportion of objects placed fewer than the indicated number of centimeters from the study location or from the T2 retrieved location. Recalled locations were within 1 cm of the T2 retrieved location much more often then they were within 1 cm of the study location.
- Figure 4.
Electrophysiological results. ERPs recorded at session 2 were computed for objects in the Active condition placed closer to (solid lines) or farther from (dotted lines) the corresponding study or T2 locations. A, Current accuracy reflects distance objects were placed from the original location at T2. B, Future accuracy reflects distance objects were placed from the original location at T3. C, Future retrieval bias reflects distance objects were placed from the T2 retrieved location at T3. ERPs from two frontal (F3 and F4) and two parietal (P3 and P4) locations are displayed.
- Figure 5.
Topographic maps. A–C, Individual maps depict mean amplitude differences at 400–700 ms and 700–1000 ms for the contrast current accuracy (A), the contrast future accuracy (B), and the contrast future retrieval bias (C). Whereas differences tended to be relatively larger at frontal locations for the current accuracy contrast at 400–700 ms, differences were pronounced at most scalp locations at 700–1000 ms for the future retrieval bias contrast.
Tables
Above median (closer) Median Below median (farther) Current accuracy 1.89 (0.27) 3.64 (1.05) 7.57 (0.62) Future accuracy 2.01 (0.24) 3.74 (1.08) 7.84 (0.59) Future retrieval bias 0.99 (0.13) 2.14 (0.62) 6.19 (0.67) For each contrast, trials were distributed into two conditions (Closer/Farther) according to distance measurements. These distance measurements were obtained on the basis of current accuracy, future accuracy, and future retrieval bias. The distance between the T2 recalled location and the study location was used for current accuracy. The distance between the T3 recalled location and the study location was used for future accuracy. The distance between the T3 recalled location and the T2 recalled location was used for future retrieval bias. Trials were assigned to conditions according to whether distances were smaller or greater than the median. Distance values are shown as averaged across participants (measured in centimeters, with SEM).
