Reactivation of Previous Experiences in a Working Memory Task

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.