Article: Brain dysfunction blamed for drug addiction

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Brain dysfunction blamed for drug addiction

20 August 2007
Stuff News

Drug users who can't kick the habit can blame a dysfunctional brain for their addiction, according to new research.

A study by the University of Melbourne has found long-term drug users have more difficulty controlling impulses because their frontal cortex is impaired.

The two-year study found opiate users needed to use more of their brains to resist impulses in a test of self control than those who were clean.
The findings shed new light on why drug addicts find it so hard to quit, despite the health consequences.

"Drugs can capture and hijack some parts of the brain," said Dr Murat Yucel, a lead researcher in the study.

"In this study we found the frontal cortex, an area that is essential for exercising control over thoughts and behaviours, was working inefficiently. "These findings may help explain why it takes addicted individuals enormous effort to exercise control over their drug taking behaviour in the face of adverse consequences and why they are vulnerable to relapse back into uncontrolled, compulsive patterns of use."

The study - published in the journal, Molecular Psychiatry, last month - also found drug users' brain cells in the frontal region were less healthy than normal.

The research shows drug taking is not a matter of choice for long-term users, who have a reduced biological capacity to stop, Dr Yucel says.

Researchers will next examine whether reduced brain function is a consequence of addiction or a contributing factor that makes some people more vulnerable to drug abuse.

Co-researcher Dan Lubman said the study would likely lead to the development of new strategies for the treatment of addiction.

"These findings tell us that we need to provide a combination of pharmaceutical and psychological treatments that will help bolster the efficiency of the frontal cortex and hence the individual's ability to stop their urge to use drugs," he said.

http://www.stuff.co.nz/stuff/4171547a7144.html

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Area responsible for 'self-control' found in the human brain - May help explain why some people are impulsive

WASHINGTON, DC
August 15, 2007
eurekalert

The area of the brain responsible for self-control—where the decision not to do something occurs after thinking about doing it—is separate from the area associated with taking action, scientists say in the August 22 issue of The Journal of Neuroscience.

“The results illuminate a very important aspect of the brain's control of behavior, the ability to hold off doing something after you've developed the intention to do it—one might call it ‘free won't’ as opposed to free will,” says Martha Farah, PhD, of the University of Pennsylvania. “It is very important to identify the circuits that enable ‘free won’t’ because of the many psychiatric disorders for which self-control problems figure prominently—from attention deficit disorder to substance dependence and various personality disorders.” Farah was not involved in the experiment.

The findings broaden understanding of the neural basis for decision making, or free will, and may help explain why some individuals are impulsive while others are reluctant to act, says lead author Marcel Brass, PhD, of the Max Planck Institute for Human Cognitive and Brain Sciences and Ghent University. Brass and Patrick Haggard, PhD, of University College London, used functional magnetic resonance imaging (fMRI) to study the brain activity of participants pressing a button at times they chose themselves.

They compared data from these trials to results when the participants prepared to hit the button, then decided to hold back or veto the action.
Fifteen right-handed participants were asked to press a button on a keyboard. They were asked to choose some cases in which they stopped just before pressing the button. Participants also indicated on a clock the time at which they intended to press the button or decided to hold back.

When Brass and Haggard compared fMRI images of the two scenarios, they found that pulling back yielded activity in the dorsal fronto-median cortex (dFMC), an area on the midline of the brain directly above the eyes, which did not show up when participants followed through and made the action.

In addition, those who chose to stop the intended action most often showed greatest contrast in dFMC activity. “The capacity to withhold an action that we have prepared but reconsidered is an important distinction between intelligent and impulsive behavior,” says Brass, “and also between humans and other animals.”

Future study will involve methods with a better time resolution such as EEG to determine whether the inhibitory process could operate in the brief time period between the time of conscious intention and the point of no return for motor output.

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The work was supported by the German Research Foundation.
The Journal of Neuroscience is published by the Society for Neuroscience, an organization of more than 36,500 basic scientists and clinicians who study the brain and nervous system.

http://www.eurekalert.org/pub_releas...arf081507.php#