A distinct alpha-wave pattern occurs in two brain regions just before subjects make mistakes on attention-demanding tests, according to a study published in the March 23 online issue of Human Brain Mapping. Researchers at the University of California, Davis, in collaboration with the Donders Institute in the Netherlands, have found an electric signature in the brain which predicts such an error.
The discovery could prove useful in a variety of applications, from developing monitoring devices that alert air traffic control operators that their attention is flagging, to devising new strategies to help children cope with attention deficit hyperactivity disorder (ADHD).
"What I was looking for was the state the brain is in before a mistake is made because that's what can tell us what produces the error," said Ali Mazaheri, a research fellow at the UC Davis Center for Mind and Brain.
Working with colleagues at the Donders Institute for Brain, Cognition and Behavior at Radboud University, where he was a PhD student at the time, Mazaheri recruited 14 students into his study. During a test, Mazaheri recorded their brain activity using magnetoencephalography (MEG) a non-invasive brain-wave recording technique similar to, but more sensitive than electroencephalography (EEG).
The test, known as the "sustained attention response task," was developed in the 1990s to evaluate brain damage, ADHD and other neurological disorders. Participants sit at a computer for an hour, and a random number from one to nine flashes on the screen every two seconds. The object is to tap a button as soon as any number except five appears. The test is so monotonous, Mazaheri said, that even when a five showed up, his subjects spontaneously hit the button an average of 40 percent of the time.
By analyzing the recorded MEG data, the research team found that about a second before the errors were committed, brain waves in two regions were stronger than when the subjects correctly refrained from hitting the button. In the occipital region, alpha wave activity was about 25 percent stronger, and in the middle region, the sensorimotor cortex, there was a corresponding increase in the brain's mu wave activity.
"The alpha and mu rhythms are what happen when the brain runs on idle," Mazaheri explained. "Say you're sitting in a room and you close your eyes. That causes a huge alpha rhythm to rev up in the back of your head. But the second you open your eyes, it drops dramatically, because now you're looking at things and your neurons have visual input to process."
The team also found that errors triggered immediate changes in wave activity in the front region of the brain, which appeared to drive down alpha activity in the rear region, "It looks as if the brain is saying, 'Pay attention!' and then reducing the likelihood of another mistake," Mazaheri said.
It should not take too many years to incorporate these findings into practical applications, according to Mazaheri. For example, a wireless EEG could be deployed at an air traffic controller's station to trigger an alert when it senses that alpha activity is beginning to regularly exceed a certain level.
It could also provide new therapies for children with ADHD, he said. "Instead of watching behavior - which is an imprecise measure of attention - we can monitor these alpha waves, which tell us that attention is waning. And that can help us design therapies as well as evaluate the efficacy of various treatments, whether it's training or drugs."