Using an electroencephalogram (EEG) — a test that measures electrical activity in the brain — researchers are able to tell whether a person with attention-deficit hyperactivity disorder (ADHD) has the inattentive or hyperactive subtype, according to a new study published in the journal Biological Psychiatry.
For the study, teens between the ages of 12 and 17 were asked to perform computer tasks that involved perceiving a visual stimulus that would then trigger brain regions involved in decision-making, which then led to physical action — in this case, pressing a button.
Researchers found that the 17 participants that were predominantly diagnosed with the inattentive (IA) subtype of ADHD had the least amount of alpha wave suppression — necessary to filter out visual “noise” in order to make an accurate decision.
On the other hand, the 17 participants diagnosed with the combined subtypes (CB) — those with symptoms of both inattention and impulsivity/hyperactivity — had the least amount of beta wave suppression, suggesting that these teens had the most trouble with the motor task.
Ali Mazaheri, Ph.D., an assistant professor at the Academic Medical Center, University of Amsterdam, and colleagues at the University of California Davis noted growing research showing that alpha wave activity can be adjusted and enhanced through rhythmic transcranial magnetic stimulation or transcranial alternating stimulation.
The teens’ brain waves were evaluated with EEG caps with 32 electrodes. Some cues were more helpful than others, so the task required the participants to occasionally override an initial impulse in order to make a correct response. Such situations are particularly challenging for people with ADHD, said the researchers.
The findings showed that the 23 typically developing (TD) teens had the quickest response times and the most correct responses compared with the other two groups. The CB group had the lowest number of correct answers and the slowest response times. And both the TD and IA groups had significantly faster reaction times than the CB group.
Researchers found that these differences among the groups correlated with different brain waves patterns, suggesting that these groups have distinct physiological profiles.
Researchers found similar results regarding beta wave changes in the brain’s motor cortex.
The greatest amount of beta suppression occurred in the TD group while the CB group had the least amount of beta suppression. The difference between the IA and CB groups was not significant.
“Our study suggests differential impairment profiles in the ADHD subtypes, and not simply an additive effect of impairments in the ADHD combined subtype,” said co-author Catherine Fassbender, Ph.D., a research scientist with the UC Davis MIND Institute, in a statement.
“The inattentive group had problems processing the cues, whereas the combined type had problems using the cues to prepare a motor response,” she said.
Source: Biological Psychiatry