A new study with Matt Panichello investigates how the brain controls the contents of working memory.
We trained monkeys to switch between two tasks. In one task, they selected one item from a set of items held in working memory. In the second, they attending to one stimulus in an array of visual stimuli. Neural recordings showed that similar representations in prefrontal cortex encoded the control of both selection and attention, suggesting prefrontal cortex may be a 'domain-general' controller. In contrast, attention and selection were represented independently in parietal and visual cortex.
Our recordings also showed selection acts by dynamically transforming memories between subspaces of neural activity. Early in the trial, monkeys had to remember to color of two items independently. Reflecting this, we found the memory of each item was represented in its own subspace. These subspaces were orthogonal to one another, helping to minimize interference.
Later in the trial, the monkey selected one of the items from working memory and then reported its color. This selection process dynamically transformed the representation of the item, aligning it with a common subspace. This allowed the color of the selected item to be 'read-out' (regardless of which item was selected). These results argue for a dynamic mechanism supporting cognitive control -- by dynamically transforming representations between different subspaces, cognitive control can determine what and when cognitive computations are engaged.
Full manuscript available at Nature.