Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Deficits in brain's reward system observed in ADHD patients

10.09.2009
Low levels of dopamine markers may underlie symptoms; implications for treatment

A brain-imaging study conducted at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory provides the first definitive evidence that patients suffering from attention deficit hyperactivity disorder (ADHD) have lower-than-normal levels of certain proteins essential for experiencing reward and motivation.

"These deficits in the brain's reward system may help explain clinical symptoms of ADHD, including inattention and reduced motivation, as well as the propensity for complications such as drug abuse and obesity among ADHD patients," said lead author Nora Volkow, Director of the National Institute on Drug Abuse and a long-time collaborator on neuroimaging research at Brookhaven Lab.

The study, published in the September 9, 2009, issue of the Journal of the American Medical Association, also has important implications for treatment. "Finding ways to address the underlying reward-system deficit could improve the direct clinical outcome of ADHD, and potentially reduce the likelihood of other negative consequences of this condition," said study co-author Gene-Jack Wang, chair of Brookhaven's medical department.

Prior to this study, it was not clear whether people with ADHD had abnormalities in the brain's dopamine-mediated motivation/reward system. Previous studies were relatively small and may have been complicated by the fact that some ADHD patients had undergone treatments, or had a history of drug abuse or other conditions that can affect the dopamine system.

To strengthen the statistics and control for these factors, the current study looked at 53 adult ADHD patients who had never received treatment and 44 healthy control subjects — all of whom had been carefully screened to eliminate potentially confounding variables.

The scientists used positron emission tomography (PET) to measure two markers of the dopamine system — dopamine receptors, to which the chemical messenger binds to propagate the "reward" signal, and dopamine transporters, which take up and recycle excess dopamine after the signal is sent.

Lying in a PET scanner, each patient was injected with a minute amount of a "radiotracer" compound — a chemical labeled with a radioactive form of carbon and designed to bind specifically to one of the targets. Different tracers were used for each target, and patients were scanned for each at separate times. By detecting the signal from the radiotracers, the PET machine can measure the receptor and transporter locations and concentrations in various parts of the brain.

The results clearly showed that, relative to the healthy control subjects, the ADHD patients had lower levels of dopamine receptors and transporters in the accumbens and midbrain — two key regions of the brain directly involved in processing motivation and reward. In addition, the measurements of dopamine markers correlated with measures of behavior and clinical observations of ADHD symptoms, such as reduced levels of attention as measured by standard psychological tests.

"Our findings imply that these deficits in the dopamine reward pathway play a role in the symptoms of inattention in ADHD and could underlie these patients' abnormal responses to reward," Volkow said.

"This pathway plays a key role in reinforcement, motivation, and in learning how to associate various stimuli with rewards," she continued. "Its involvement in ADHD supports the use of interventions to enhance the appeal and relevance of school and work tasks to improve performance.

"Our results also support the continued use of stimulant medications — the most common pharmacological treatment for ADHD — which have been shown to increase attention to cognitive tasks by elevating brain dopamine," she said.

The findings may also help explain why ADHD patients are more likely than control subjects to develop drug-abuse disorders and conditions such as obesity.

Said Wang: "Other studies from our group suggest that patients who abuse drugs or overeat may be unconsciously attempting to compensate for a deficient reward system by boosting their dopamine levels. Understanding how deficits in the dopamine system contribute to ADHD and finding ways to improve the functioning of the reward system could help mitigate these troubling consequences in the ADHD patient population."

This research was supported by the National Institute on Alcohol Abuse and Alcoholism Intramural Research Program and by the National Institute on Mental Health. The Office of Biological and Environmental Research within DOE's Office of Science provides infrastructure support for the radiotracer chemistry and imaging facilities at Brookhaven Lab. Brain-imaging techniques such as PET are a direct outgrowth of DOE's long-standing investment in basic research in chemistry, physics, and nuclear medicine.

Karen McNulty Walsh | EurekAlert!
Further information:
http://www.bnl.gov

More articles from Studies and Analyses:

nachricht First form of therapy for childhood dementia CLN2 developed
25.04.2018 | Universitätsklinikum Hamburg-Eppendorf

nachricht Do microplastics harbour additional risks by colonization with harmful bacteria?
05.04.2018 | Leibniz-Institut für Ostseeforschung Warnemünde

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: BAM@Hannover Messe: innovative 3D printing method for space flight

At the Hannover Messe 2018, the Bundesanstalt für Materialforschung und-prüfung (BAM) will show how, in the future, astronauts could produce their own tools or spare parts in zero gravity using 3D printing. This will reduce, weight and transport costs for space missions. Visitors can experience the innovative additive manufacturing process live at the fair.

Powder-based additive manufacturing in zero gravity is the name of the project in which a component is produced by applying metallic powder layers and then...

Im Focus: Molecules Brilliantly Illuminated

Physicists at the Laboratory for Attosecond Physics, which is jointly run by Ludwig-Maximilians-Universität and the Max Planck Institute of Quantum Optics, have developed a high-power laser system that generates ultrashort pulses of light covering a large share of the mid-infrared spectrum. The researchers envisage a wide range of applications for the technology – in the early diagnosis of cancer, for instance.

Molecules are the building blocks of life. Like all other organisms, we are made of them. They control our biorhythm, and they can also reflect our state of...

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Getting electrons to move in a semiconductor

25.04.2018 | Physics and Astronomy

Reconstructing what makes us tick

25.04.2018 | Physics and Astronomy

Cheap 3-D printer can produce self-folding materials

25.04.2018 | Information Technology

VideoLinks
Science & Research
Overview of more VideoLinks >>>