Executive control processes underlying multi-item working memory

The authors recorded activity of prefrontal cortex neurons in monkeys performing a multi-item color change detection task and found that neurons reported information about the item's position and the location covert attention, but not its color. Increased power in the local field potential correlated with more precise color representations. Taken together, these results suggest that PFC controls the allocation of resources in working memory. A dominant view of prefrontal cortex (PFC) function is that it stores task-relevant information in working memory. To examine this and determine how it applies when multiple pieces of information must be stored, we trained two subjects to perform a multi-item color change detection task and recorded activity of neurons in PFC. Few neurons encoded the color of the items. Instead, the predominant encoding was spatial: a static signal reflecting the item's position and a dynamic signal reflecting the subject's covert attention. These findings challenge the notion that PFC stores task-relevant information. Instead, we suggest that the contribution of PFC is in controlling the allocation of resources to support working memory. In support of this, we found that increased power in the alpha and theta bands of PFC local field potentials, which are thought to reflect long-range communication with other brain areas, was correlated with more precise color representations.