Shifting-related brain magnetic activity in attention-deficit/hyperactivity disorder

Current theories suggest a role for frontal-striatal circuits in the pathogenesis of attention-deficit/hyperactivity disorder (ADHD).

We used magnetoencephalography (MEG) to measure event-related brain activity during a simplified version of the Wisconsin Card Sorting Test in children with DSM-IV combined type ADHD (ADHD-C) or predominantly inattentive type ADHD (ADHD-PI) and in age- and intelligence-matched control children.

In control children, set-shifting cues evoked a higher degree of activation in the medial temporal lobe (MTL) between 200 and 300 msec than non-shifting cues, with MTL activation predicting later activity in left anterior cingulate cortex (ACC) (at 400-500 msec). This MTL-ACC response pattern was diminished in children with ADHD. By contrast, children with ADHD showed early activity in regions barely activated in control children, such as left inferior parietal lobe and posterior superior temporal gyrus.

These preliminary data support theories of frontal dysfunction in ADHD but also suggest that deficits in higher-level functions might be secondary to disruptions in earlier limbic processes.