Prospective task knowledge improves working memory-guided behaviour

Abstract

Working memory (WM) is the ability to keep information online for a forthcoming task. WM theories have tended to focus on how sensory information is maintained, and less on how WM content is used for guiding behaviour. Here we ask if WM is supported by a transformation of sensory memoranda into task-sets that are optimised for task-dependent responses. Thirty participants performed two different WM tasks; they remembered the tilt of oriented bars for either a rotation-discrimination task or a change-detection task. Task context was instructed either in advance (fixed task blocks) or at probe onset (mixed task blocks). If WM content is configured in a task-dependent format, performance should benefit from foreknowledge of the upcoming task. In line with this prediction, we found that WM accuracy was higher when participants had advance knowledge of the task context. Even if WM content can be configured as a task-set, perhaps only one item is optimised for guiding behaviour. If so, retro-cued prioritization may be supported by a transformation of the selected item from a sensory to a task-oriented code. We included a retro-cue on half of the trials to test the second hypothesis that task-foreknowledge enhances retro-cued prioritization. Interestingly, the benefits of task foreknowledge were independent of the benefits incurred by retro-cueing, indicating that attentional selection is sufficient for prioritization of WM content. Together, these results provide preliminary evidence that WM coding may be task-dependent, but neuroimaging studies are needed to elucidate the precise mechanisms by which task foreknowledge facilitates WM-guided behaviour.