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Detailed Brain Scans Show ADHD Impairment
> 11/6/2007 9:00:04 AM

PBS, a neutral forum by charter, has a page on its website for presenting the views of those who claim that ADHD is a fraudulent concept. They display an interview with Peter Breggin, who claims that: "Parents have also been lied to: flat-out lied to. They've been told that children have a neuro-biological disorder." This sort of opposition to a diagnosis thrives when scientists lack biological markers that they can use as proof that they have identified a real disorder and not just an opportunity for drug manufacturers. That is why a new fMRI study in the American Journal of Psychiatry is so important for dispelling doubts about the nature of ADHD.

Dr. Michael Stevens designed his AJP study to explore regions of the brain that were previously identified as having abnormal event-related potentials (ERPs) in ADHD subjects performing attention tasks. ERP studies have reported conflicting results, so Dr. Stevens stepped in to settle the dispute with fMRI scans. The greater precision of fMRI furthers research, and it gives doctors an intelligible and vivid picture that can be shown to doubters. Parents worried about wrongly labeling their children may be relieved by a clear 3-D video of the abnormality that requires medication, or the lack of brain abnormality that may only require patience.

Dr. Stevens scanned 23 ADHD and 23 control subjects, a large sample size for an expensive method that can malfunction at the slightest head-movement. Each subject was asked to listen to a sequence of stimuli, and to pick the target stimulus out of a series of normal and novel sounds. The ADHD group took longer to respond to the target stimuli, but this distracted behavior has already been quantified many times. The truly interesting finding was that ADHD subjects displayed impairments in the left middle frontal gyrus and the right superior temporal gyrus when listening to target stimuli, and in the left inferior parietal lobule/supramarginal gyrus and the posterior region of the left superior temporal gyrus when listening to novel stimuli. All of these regions have been linked to systems for allocating attention, and impaired stimulation may indicate that ADHD brains are unable to differentially assign importance to normal and significant stimuli, making the hum of an air-conditioner and the voice of a teacher equally engrossing.

These findings are important for dispelling doubts about the existence of a biological basis for ADHD, as well as for narrowing in on the cause of ADHD. Now that we know what brain regions are impaired, we can begin looking for a larger mechanism that interferes with all of them, such as dopamine, or we may find that there are multiple possible subtypes that can add up to behavioral problems that look similar. We can use fMRI information to start ruling out some hypotheses, such as the contention that ADHD is really an attitude problem or a lack of motivation that brings subjects to answer poorly on tests. If future researchers raise the the level of motivation, say by offering a video-game as a prize, and still see impairments in attention regions and none in motivation regions, then they can rule out that hypothesis and get one step closer to the true explanation.

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