thick brains

Blame brain cells for lack of focus
Scientists discover a neuronal network that may affect attention abilities

By Laura Sanders

Web edition : 4:58 pm 

Easily distracted people can stop blaming their lack of focus on the royal wedding, Facebook feeds and hilarious YouTube videos of honey badgers. Rather, a small network of cells in the back left part of the brain may be the culprit, researchers report in the May 4 Journal of Neuroscience.

Knowing how the brain focuses on what’s important — and filters out noise — may help scientists come up with ways to counteract attention disorders.

“Attention has a huge effect on our lives,” says cognitive neuroscientist Carmel Mevorach of the University of Birmingham in England, who was not involved in the study. “Everything we do — literally, everything we do — is affected by attention.”

In this age of information overload, appropriating attention is a challenge, says study coauthor Ryota Kanai of University College London, and some people are much more susceptible to distractions. Kanai and his colleagues wanted to know if brain differences could explain why some people are easily distracted while others stay focused.

For the study, 145 volunteers filled out a survey called the Cognitive Failures Questionnaire, which asks people to rate how frequently they experience mental lapses such as forgetting what they came to a shop to buy or bumping into people. Volunteers’ answers were used to calculate each person’s overall susceptibility to distraction in everyday life. (Incidentally, scores on the same questionnaire also predict how many car accidents someone has.)

Brain scans revealed a difference between people at the two ends of the “distractibility” spectrum: Easily distracted people had denser tissue in a region called the superior parietal cortex on the left side of the head, signaling that there are more nerve cells there. 

“The idea that you can actually ask people to rate their distractibility and that it can lead to a particular place in the brain is quite interesting,” Mevorach says. 

The finding that people who have trouble paying attention actually have more brain tissue in that region is somewhat counterintuitive, but bigger isn’t always better. As the brain matures, Kanai says, irrelevant nerve cell connections are pruned, so easily distracted people could be missing some brain refinement important for attention control.

To test whether this brain region actually influenced distraction — and wasn’t just associated with it — Kanai and his colleagues temporarily disrupted brain function there in 15 volunteers using a technique called transcranial magnetic stimulation. In what Kanai calls a “psychologist’s version of Where’s Waldo?” people hunt for a circle and filter out irrelevant details, such as a distracting red diamond. With dampened brain activity in the left superior parietal cortex, people took longer to find the target than when  brain activity was not reduced, suggesting that this brain region influences attention. Dampening activity in an unrelated part of the brain didn’t have an effect.

Although the new results are convincing, there is still a lot to learn about how the brain pays attention, says neuroscientist Adam Gazzaley of the University of California, San Francisco. “All of these things are pieces of the puzzle of how a very complicated brain interacts with our environment.”