Abstract
Visual objects separated in time are not processed independently from each other. Instead, a current object is often reported as more similar to a previously encoded, but now irrelevant object than it actually was. This phenomenon is called serial dependence. Until now, it has remained unclear whether serial dependence occurs during an early stage in the object processing hierarchy, i.e., when an object is encoded into the visual system, or during later stages, i.e., when an object is retained in working memory or selected for an action. To determine at which stage an object representation becomes biased, we recorded neuronal activity using MEG while subjects encoded and memorized two sequentially presented motion directions and, after a short delay, selected one direction for a report based on a retro-cue. Using a model-based MEG decoding approach, we found that the neural representation of a current motion direction was shifted toward the previous motion direction only after the retro-cue, when a direction was selected for subsequent report. On a single-trial level, the shift of the decoded motion direction after the retro-cue predicted the magnitude and direction of subjects’ response errors during continuous recall. These results show that an object representation is susceptible to serial dependence especially during a late stage of object processing, when it changes its format from a representation that is memorized for potential use to a representation that is already selected and prepared for upcoming action.