Working memory is a sort of "mental sketchpad" that allows you to accomplish everyday tasks such as calling in your hungry family's takeout order and finding the bathroom you were just told "will be the third door on the right after you walk straight down that hallway and make your first left." It also allows your mind to go from merely responding to your environment to consciously asserting your agenda. "Working memory allows you to choose what to pay attention to, choose what you hold in mind, and choose when to make decisions and take action," says Earl K. Miller, the Picower Professor in MIT's Picower Institute for Learning and Memory and the Department of Brain and Cognitive Sciences. "It's all about wresting control from the environment to your own self. Once you have something like working memory, you go from being a simple creature that's buffeted by the environment to a creature that can control the environment."
For years Miller has been curious about how working memory—particularly the volitional control of it—actually works. In a new study in the Proceedings of the National Academy of Sciences led by Picower Institute postdoc Andre Bastos, Miller's lab shows that the underlying mechanism depends on different frequencies of brain rhythms synchronizing neurons in distinct layers of the prefrontal cortex (PFC), the area of the brain associated with higher cognitive function. As animals performed a variety of working memory tasks, higher-frequency gamma rhythms in superficial layers of the PFC were regulated by lower-frequency alpha/beta frequency rhythms in deeper cortical layers. The findings suggest not only a general model of working memory, and the volition that makes it special, but also new ways that clinicians might investigate conditions such as schizophrenia where working memory function appears compromised.