Executive Networks Differ in Those with ADHD

The complex cognitive processes I have described thus far are not specific to persons with ADD syndrome; these structures and neurochemicals manage brain functions in all of us. Over recent years researchers have begun to accumulate evidence, especially from brain imaging studies, of some differences in brain development and functioning in those who suffer from ADD syndrome.

One of the earliest studies of differences in brain functioning of persons with ADHD was provided in 1990 by Alan Zametkin and colleagues. They used imaging to compare levels of chemical activity in the brains of adults with and without a history of hyperactivity since childhood. Results indicated that when adults with ADHD did a task that required sustained concentration, they demonstrated a lower rate of chemical activity, both globally and in specific regions of the brain, than did normal controls. Brains of those with ADHD were less "turned on" while doing the concentration task than were the matched controls.

Monique Ernst and others (1999) did an imaging study that compared brains of children with ADHD to normal controls. These images showed that children with ADHD had an abnormality in the processing of dopamine in their midbrain regions. Sarah Durston (2003) used a different imaging method to study self-control systems in children with ADHD compared to normal children. While in the scanner, each child was asked to press a button each time a particular Pokemon cartoon character appeared on a screen and to avoid pushing the button each time another Pokemon character appeared. Children with ADHD had great difficulty in holding back their button press in the "avoid pushing" situation if it was preceded by even just one "push" signal. The brain scans showed that while doing this task children with ADHD also showed a more immature pattern of brain activation; their brain activity was more characteristic of patterns in younger children.

Imaging studies have also shown that many with ADHD use different, less efficient circuits of the brain to do certain cognitive tasks. George Bush and colleagues (1999) observed brain activity in a specific area, the anterior cingulate (shown in Figure 3), in adults with ADHD while they were doing a simple task that required resolving conflicting information. When the brain activity of the ADHD adults on this task was compared with that of a matched sample of non-ADHD adults, there was a significant difference when distracters were present. Non-ADHD adults showed significant activation of the anterior cingulate region most persons use for resolving such conflicts. By contrast, those with ADHD showed almost no activation anywhere in the anterior cingulate when confronted with dis-tracters while doing this task; instead, totally separate circuits were employed and the result was a significantly slower response. It is as though the ADHD adults, when they were being distracted, had to use a slower, detour circuit to accomplish the task.

Ernst and others (2003) showed another difference between the brain functioning of individuals with ADHD and those without. They used imaging scans to observe brains of adults with ADHD and age-matched healthy volunteers as they were making decisions about the relative importance of alternative rewards. These adults were asked to make a series of choices that involved weighing short-term gains against long-term losses. Results showed that while both groups utilized similar regions of the prefrontal cortex for making the decisions, the brains of the ADHD adults were markedly less active in regions that facilitate evaluation of the emotional attributes of stimuli. The researchers suggested that cognitive deficits in ADHD adults might interfere with their "coding of motivation," that is, their ability to assess the relative importance of one object or situation over another.

Although there are currently only a few relevant imaging studies, their results thus far suggest that there are demonstrable differences in the functioning of executive function brain circuits between persons with and without ADD syndrome. As imaging technology and understanding of this disorder improve, more refined studies should become possible. Meanwhile, however, the response of persons with ADHD to specific medications has been consistently demonstrated in many studies.

Was this article helpful?

0 0
Understanding And Treating ADHD

Understanding And Treating ADHD

Attention Deficit Disorder or ADD is a very complicated, and time and again misinterpreted, disorder. Its beginning is physiological, but it can have a multitude of consequences that come alongside with it. That apart, what is the differentiation between ADHD and ADD ADHD is the abbreviated form of Attention Deficit Hyperactive Disorder, its major indications being noticeable hyperactivity and impulsivity.

Get My Free Ebook

Post a comment