Reactivation of Previous Experiences in a Working Memory Task

Abstract

Recent experiences influence the processing of new information even when those experiences are irrelevant to the current task. Does this reflect the indirect effects of a passively maintained representation of the previous experience, or is this representation reactivated when a new event occurs? To answer this question, we attempted to decode the orientation of the stimulus on the previous trial from the electroencephalogram on the current trial in a working memory task. Behavioral data confirmed that the previous-trial stimulus orientation influenced the reported orientation on the current trial, even though the previous-trial orientation was now task irrelevant. In two independent experiments, we found that the previous-trial orientation could be decoded from the current-trial electroencephalogram, indicating that the current-trial stimulus reactivated or boosted the representation of the previous-trial orientation. These results suggest that the effects of recent experiences on behavior are driven, in part, by a reactivation of those experiences and not solely by the indirect effects of passive memory traces.

Keywords: ERP decoding; open data; previous trial decoding; serial dependence; working memory.

Fig. 1.

Example trial sequences from (a) Experiment 1 and (b) Experiment 2. In both experiments, participants first saw a sample teardrop drawn in 1 of 16 orientations. After a delay, participants reported the remembered orientation by adjusting the orientation of a test teardrop until it matched the remembered orientation. The Experiment 2 task was identical to the Experiment 1 task except that the location and the orientation of the sample teardrop were independently manipulated, and the location of the test teardrop was independent of the location of the sample teardrop. ITI = intertrial interval.

Fig. 2.

Results. In the top row, mean response error (reported orientation – sample orientation) is shown as a function of the difference between the current-trial and previous-trial orientations in (a) Experiment 1 and (b) Experiment 2. Error bars represent ±1 SE. The curves show the best-fitting first derivative-of-Gaussian function, which was used to quantify the amplitude of the serial-dependence effect (indicated by the area labeled “Amplitude”). Mean accuracy for decoding the previous-trial orientation from the current-trial scalp topography is shown for (c) Experiment 1 and (d) Experiment 2. Orange shading represents ±1 SE. Gray areas indicate clusters of time points that produced above-chance decoding after correction for multiple comparisons.