Selective control of working memory in prefrontal, parietal, and visual cortex

Cognitive control guides behavior by controlling what, where, and how information is represented in the brain. Previous work has shown parietal and prefrontal cortex direct attention, which controls the representation of external sensory stimuli. However, the neural mechanisms controlling the selection of representations held 9in mind9, in working memory, are unknown. To address this, we trained two monkeys to switch between two tasks, requiring them to either select an item from a set of items held in working memory or attend to one stimulus from a set of visual stimuli. Simultaneous neural recordings in prefrontal, parietal, and visual cortex found prefrontal cortex played a primary role in selecting an item from working memory, representing selection before parietal and visual cortex. Surprisingly, a common population representation in prefrontal cortex encoded selection of an item in working memory and attention to an external stimulus, suggesting prefrontal cortex may act as a domain-general controller. Selection acted on memory representations in two ways. First, selection improved the accuracy of memory reports by enhancing the selected item9s representation in prefrontal and parietal cortex. Second, selection transformed memory representations in a task-dependent manner. Before selection, when both items were relevant to the task, the identity of each item was represented in an independent subspace of neural activity. After selection, the representation of only the selected item was transformed into a new subspace that was used to guide the animal9s behavioral report. Together, our results provide insight into how prefrontal cortex controls working memory representations, selectively enhancing and transforming them to support behavior.