How your brain filters out distractions to focus

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A new study illustrates how parts of the brain need to work together to focus on important information while filtering out distractions.

Imagine a busy restaurant: dishes clattering, music playing, people talking loudly over one another. It’s a wonder that anyone in that kind of environment can focus enough to have a conversation.

The new research from researchers at Brown University’s Carney Institute for Brain Science provides some of the most detailed insights yet into the brain mechanisms that help people pay attention amid such distraction, as well as what’s happening when they can’t focus.

In an earlier psychology study, the researchers established that people can separately control how much they focus (by enhancing relevant information) and how much they filter (by tuning out distraction). The team’s new research in Nature Human Behaviour unveils the process by which the brain coordinates these two critical functions.

Lead author and neuroscientist Harrison Ritz likens the process to how humans coordinate muscle activity to perform complex physical tasks.

“In the same way that we bring together more than 50 muscles to perform a physical task like using chopsticks, our study found that we can coordinate multiple different forms of attention in order to perform acts of mental dexterity,” says Ritz, who conducted the study while a PhD student at Brown.

The findings provide insight into how people use their powers of attention as well as what makes attention fail, says coauthor Amitai Shenhav, an associate professor in Brown’s cognitive, linguistic, and psychological sciences department.

“These findings can help us to understand how we as humans are able to exhibit such tremendous cognitive flexibility—to pay attention to what we want, when we want to,” Shenhav says. “They can also help us better understand limitations on that flexibility, and how limitations might manifest in certain attention-related disorders such as ADHD.”

To conduct the study, Ritz administered a cognitive task to participants while measuring their brain activity in an fMRI machine. Participants saw a swirling mass of green and purple dots moving left and right, like a swarm of fireflies. The tasks, which varied in difficulty, involved distinguishing between the movement and colors of the dots. For example, participants in one exercise were instructed to select which color was in the majority for the rapidly moving dots when the ratio of purple to green was almost 50/50.

Ritz and Shenhav then analyzed participants’ brain activity in response to the tasks.

Ritz, who is now a postdoctoral fellow at the Princeton Neuroscience Institute, explains how the two brain regions work together during these types of tasks.

“You can think about the intraparietal sulcus as having two knobs on a radio dial: one that adjusts focusing and one that adjusts filtering,” Ritz says. “In our study, the anterior cingulate cortex tracks what’s going on with the dots. When the anterior cingulate cortex recognizes that, for instance, motion is making the task more difficult, it directs the intraparietal sulcus to adjust the filtering knob in order to reduce the sensitivity to motion.

“In the scenario where the purple and green dots are almost at 50/50, it might also direct the intraparietal sulcus to adjust the focusing knob in order to increase the sensitivity to color. Now the relevant brain regions are less sensitive to motion and more sensitive to the appropriate color, so the participant is better able to make the correct selection.”

Ritz’s description highlights the importance of mental coordination over mental capacity, revealing an often-expressed idea to be a misconception.

“When people talk about the limitations of the mind, they often put it in terms of, ‘humans just don’t have the mental capacity’ or ‘humans lack computing power,'” Ritz says. “These findings support a different perspective on why we’re not focused all the time. It’s not that our brains are too simple, but instead that our brains are really complicated, and it’s the coordination that’s hard.”

Ongoing research projects are building on these study findings. A partnership with physician-scientists at Brown University and Baylor College of Medicine is investigating focus-and-filter strategies in patients with treatment-resistant depression. Researchers in Shenhav’s lab are looking at the way motivation drives attention; one study co-led by Ritz and Brown PhD student Xiamin Leng examines the impact of financial rewards and penalties on focus-and-filter strategies.

Funding for the study came from the National Institutes of Health, the National Science Foundation, and by a postdoctoral fellowship from the CV Starr Foundation.

Source: Gretchen Schrafft for Brown University