Study reveals working memory is an orchestra rather than a solo act-with multiple brain regions contributing to help us maintain information
It's been long established that our working memory, which allows us to temporarily hold and use information, such as remembering a phone number or a shopping list, is largely driven by the brain's prefrontal cortex. However, new research finds that the part of the brain used in visual processing plays a much more critical role in working memory than previously thought.
The findings, which appear in the journal Nature Communications, provide new avenues for clinical study on neurological and psychiatric conditions that have working-memory impairments and point the way to more effective measures in assessing and addressing memory-related afflictions.
"Our results show that working memory isn't confined to one specific brain area, but is instead distributed across multiple regions-from the prefrontal cortex in the front to early visual cortex, which situated at the back and helps us see," explains Clayton Curtis, a professor of psychology at New York University and the paper's senior author. "This new understanding will provide additional avenues for clinical research.
"For instance, current treatments for schizophrenia primarily focus on the prefrontal cortex despite the fact that patients with schizophrenia often have perceptual problems. Moreover, the visual aspects of working memory are highly sensitive to subtle changes in brain dysfunction and tests of working memory can be used to assess the progression and response to treatments for Alzheimer's disease, multiple sclerosis, and other cognitive decline that comes with aging."
Scientists have known for almost a century that our ability to store information in working memory-the brain's "sketchpad"-depends on the prefrontal cortex. However, many questions about the intricacies of this process remain.
In an effort to enhance our understanding, Curtis and Mrugank Dake, an NYU doctoral student and the paper's lead author, considered the potential role of the early visual cortex (V1), which handles basic visual processing tasks such as recognizing shapes, orientations, and colors.
"Here, we wanted to test the hypothesis that V1 plays a critical role, not only in vision, but also in memory," explains Dake.
While previous research demonstrated that activity in V1 is correlated with visual working memory, no one knew if that activity is actually necessary for memory.
"Obviously, one could not study visual working memory abilities in people who were blind from damage to V1 as they would not be able to see the information to memorize," says Curtis.
To get around this problem, the researchers used transcranial magnetic stimulation (TMS) to briefly disrupt neural activity in V1 with strong magnetic pulses while human participants stored visual information in working memory.
In order to isolate the possible role of V1, the magnetic pulses were focused on a localized part of V1 that represents a specific area of the visual field-the equivalent of creating a temporary blind spot lasting milliseconds.
The results showed that the participants' ability to remember visual information was impaired-but only for the part of the visual field affected by TMS. For instance, if TMS targeted the portion of V1 representing the bottom-right corner of the screen, participants made more errors when recalling details from that specific area.
In addition, this disruption occurred not only when TMS was applied immediately after participants saw an image-when V1 is known to process incoming visual information-but also when TMS was applied well after the image had disappeared and when it was being stored in memory, indicating a foundational impact.
"This suggests that V1 is not merely used for seeing but is also used to actively hold onto that information for future use," explains Curtis.
"We discovered that disrupting neural activity in V1 affects visual working memory-a surprising finding given its assumed role as only a basic processor of visual information," observes Dake.
This research was supported by grants from the National Institutes of Health (R01-EY016407, R01-EY033925).
