Goal-directed modulation of neural activity during working memory maintenance.

Visual working memory is crucial for goal-directed thoughts and behaviors. However, it is not clear how goals modulate working memory maintenance, as previous models often considered stimulus encoding to be the endpoint of goal-directed control. To address this gap, eighty adults performed delayed estimation tasks while their brain activity was recorded using electroencephalography. In each trial, participants memorized three visual gratings varying in orientation and location and were instructed which attribute to recall. Based on recall success, trials were classified as successful or unsuccessful. We examined the effects of task instructions and their behavioral relevance using event-related potentials and multivariate pattern analysis during encoding and maintenance. The orientation task elicited larger contralateral delay activity than the location task. Moreover, the two tasks were decodable from brain patterns during the maintenance phase, and these patterns did not generalize to the encoding phase, suggesting that goal-directed modulation during maintenance was not merely a consequence of selective encoding. We further found that goal-directed modulation involves two functionally distinct processes that unfold dynamically over time, with the latter beginning even before stimulus offset and continuing throughout the entire maintenance phase. Finally, task decoding accuracy was consistently higher for successful than unsuccessful trials during maintenance.