Seminar: Neural Dynamics of Working Memory

Cognitive control guides behavior by controlling what, where, and how information is represented in the brain. Perhaps the most well-studied form of cognitive control has been ‘attention’, which controls how external sensory stimuli are represented in the brain. In contrast, the neural mechanisms controlling the selection of representations held ‘in mind’, in working memory, are unknown. In this talk, I will present evidence that prefrontal cortex controls working memory by selectively enhancing and transforming the contents of working memory. To show this, we trained 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, the same representation that controlled selection also directed attention to an external stimulus, suggesting prefrontal cortex may act as a domain-general controller. Furthermore, we found that selection acted on memory representations by strengthening the selected item and transforming it in a task-dependent manner. Before selection, when both items were relevant to the task, the identity of each item was represented equally in two independent subspaces of neural activity. After selection, the representation of only the selected item was strengthened and transformed into a new subspace that was used to guide the animal’s behavioral report. Together, our results show how prefrontal cortex controls working memory, selectively enhancing and transforming memories to support behavior.

This seminar will be given both in-person and online. Details in attached poster.