Disconnect Between Brain Regions in ADHD

Jan 11, 2010

(PhysOrg.com) -- Two brain areas fail to connect when children with attention deficit hyperactivity disorder attempt a task that measures attention, according to researchers at the UC Davis Center for Mind and Brain and M.I.N.D. Institute.

"This is the first time that we have direct evidence that this connectivity is missing in ADHD," said Ali Mazaheri, postdoctoral researcher at the Center for Mind and Brain. Mazaheri and his colleagues made the discovery by analyzing the in children with ADHD. The paper appears in the current online issue of the journal Biological Psychiatry.

The researchers measured electrical rhythms from the brains of volunteers, especially the alpha rhythm. When part of the brain is emitting alpha rhythms, it shows that it is disengaged from the rest of the brain and not receiving or processing information optimally, Mazaheri said.

In the experiments, children with diagnosed ADHD and normal children were given a simple attention test while their were measured. The test consisted of being shown a red or blue image, or hearing a high or low sound, and having to react by pressing a button. Immediately before the test, the children were shown either a letter "V" to alert them that the test would involve a picture (visual), or an inverted "V" representing the letter “A” to alert them that they would hear a sound (auditory).

The experiments were conducted by researchers in the laboratories of Ron Mangun, professor of psychology and neurology, and Blythe Corbett, associate clinical professor of psychiatry and behavioral sciences and a researcher at the M.I.N.D. Institute.

According to current models of how the brain allocates attention, signals from the -- such as the "V" and "A" cues -- should alert other parts of the brain, such as the visual processing area at the back of the head, to prepare to pay attention to something. That should be reflected in a drop in alpha wave activity in the visual area, Mazaheri said.

And that is what the researchers found in the brain waves of children without ADHD. But children with the disorder showed no such drop in activity, indicating a disconnection between the center of the brain that allocates attention and the visual processing regions, Mazaheri said.

"The brains of the children with ADHD apparently prepare to attend to upcoming stimuli differently than do typically developing children," he said.

with ADHD did improve their reaction times when properly cued, but they don't seem to allocate resources as efficiently, Mazaheri said.

This is the first evidence from electrical patterns for a functional disconnection in cortical attention systems in ADHD, he said. Current definitions of ADHD are based only on behavior.

The research was originally inspired by a desire to combine laboratory and clinical research to go beyond existing measures of ADHD and get a better understanding of the condition, Corbett said.

"Clearly the crosstalk from bedside to bench has been fruitful," she said.

Other co-authors on the paper are staff research associate Sharon Corina, postdoctoral fellow Evelijn Bekker and research assistant Anne Berry.

The study was funded by the grants from the National Institutes of Health, the Netherlands Organization for Scientific Research, the Perry Family Foundation, the Debber Family Foundation and the Aristos Academy.

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User comments : 4

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1epi
1 / 5 (3) Jan 11, 2010
idi*ts... there is not such thing as ADHD. only happy, healty kids. you turn them in patients in order to get as much money as you can from this non existent disease.
Lolipop
5 / 5 (1) Jan 11, 2010
1epi

ADHD is not a disease - it's a personality trait. But some traits are not very pleasant to live with: my attention is actually getting better with Ritalin. My impulsive behaviour get better. I FEEL, FINALLY, GOOD ABOUT MYSELF. I can read, I can go out and speak with people without getting sweaty. It's working.
xenocog
not rated yet Jan 12, 2010
ADHD is a cognitive style mediated by neurology, not a personality trait and certainly not imaginary. It is also not a deficit of attention despite its name: it is a deficit of the ability to control one's attention. Many ADHD people routinely hyperfocus on preferred activities like video games or reading. It is the inability to focus on non-preferred activities like homework that cause a problem. There are also problems with organization and impulsivity. There are also well-known co-morbidities: depression and drug abuse top the list, and all three may well be related to the neurotransmitter dopamine. As I understand it, the Ritalin mentioned in the post by Lolipop works because it up-regulates dopamine in the prefrontal cortex, an area of the brain that is involved with executive function --in other words, self-regulatory behavior. By being dopaminergic, it also has a tendency to improve mood.
Lolipop
not rated yet Jan 15, 2010
xenocog

I just wanted to sound diplomatic. I think it's a part of my personality, though. That's why I called it a personality trait and not a disorder. A disorder is a trait which makes your life suck in some area(s) - ADHD is one of them.

1epi

To call my trait non-existing or "only happy, healty kids" is like calling psychopathy or eating disorders the same. Why isn't that a problem for you?

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