Revisiting the role of persistent neural activity during working memory

• Recent work suggests that the standard neural model of WM is in need of revision.
• Multivariate analyses find that sensory cortex stores WM information.
• lPFC simultaneously encodes multiple task variables to bias sensory regions.
• WM is mediated by dynamic population codes in addition to persistent neural activity.

What are the neural mechanisms underlying working memory (WM)? One influential theory posits that neurons in the lateral prefrontal cortex (lPFC) store WM information via persistent activity. In this review, we critically evaluate recent findings that together indicate that this model of WM needs revision. We argue that sensory cortex, not the lPFC, maintains high-fidelity representations of WM content. By contrast, the lPFC simultaneously maintains representations of multiple goal-related variables that serve to bias stimulus-specific activity in sensory regions. This work highlights multiple neural mechanisms supporting WM, including temporally dynamic population coding in addition to persistent activity. These new insights focus the question on understanding how the mechanisms that underlie WM are related, interact, and are coordinated in the lPFC and sensory cortex.