Children with Attention Deficit Hyperactivity Disorder (ADHD) have serious problems to control behavioral inhibition, also known as interference control. The functional brain activity that underlies this cognitive process, however, remains contested.
Zamorano et al. (2017) performed a functional neuroimaging study with boys with and without ADHD to address this question using the multi source interference task (MSIT).
This task presented the children with three numbers in a line, one of which was different from the other two. They had to report the different number by pressing the button of the number on the keypad. In one condition (congruent) the position of the number on the screen matched the position of the number on the keypad, and in the other condition (incongruent), the position of the number on the screen did not match the position of the number on the keypad. By contrasting the incongruent to the congruent condition, the researchers were able to identify the “MSIT effect”, which shows what happens while children are dealing with the incongruence (or interference).
Overall, behavioral results showed that both groups performed similarly on the task, although ADHD boys committed more mistakes than typically developing (TC) boys. Also, ADHD children presented a bigger MSIT effect, reflected in larger difference of reaction time between both conditions. Moreover, the activation associated to the MSIT effect showed greater activation in right lateral prefrontal cortex (rlPFC) in ADHD than in TC boys. Finally, the ADHD children showed greater functional connectivity between rlPFC and bilateral orbitofrontal cortex than the TD children. This difference in connectivity also correlated with worse performance in both groups. The authors suggest that these results could reflect a compensatory strategy of ADHD children that results from their attempt to solve the task and that permits them to perform similarly to TD children in the task.
This research contributes to a better understanding of the frontal brain regions on that ADHD children rely on when solving this kind of interference control task. Also, it shows that children with ADHD activate compensatory brain mechanisms that allow them to achieve a similar performance on this task as compared to TD children. These results remind us of the importance of conducting neurophysiological studies along with neuropsychological evaluations with this clinical population in order to better understand the etiology of this disorder.