New insight on rehabilitating brain function in addicts

Jan 28 2011

People with addictions to stimulants tend to choose instant gratification or a smaller but sooner reward over a future benefit, even if the future reward is greater. Reduced value of a future reward, called "delay discounting" by neuroscientists, is the major challenge for treatment of addiction. A new study in the February 2011 (Vol. 69, Issue 3) Biological Psychiatry appears to present a strategy for increasing the value of future rewards in the minds of addicts.

"The hope is for a new intervention to help addicts," said Warren K. Bickel, professor and director of the Center for Substance Abuse at the Virginia Tech Carilion Research Institute effective Feb 1. 2011. Bickel will also be a professor in the Department of Psychology at Virginia Tech.

Bickel did the research when he was the Wilbur D. Mills Chair of Alcoholism and Drug Abuse Prevention and director of the Center for Addiction Research and the Center for the Study of Tobacco Addiction at the University of Arkansas for Medical Sciences.

"It is a major coup for us to be able to attract Dr. Bickel to the Virginia Tech Carilion Research Institute and Roanoke. He is a renowned research leader in understanding the strategies used by the human brain during addiction and his latest work is providing valuable new insights into potential therapeutic strategies for rehabilitating the addicted human brain," said Michael Friedlander, executive director of the research institute.

According to studies by Bickel and colleagues at the at the University of Arkansas for Medical Sciences, consideration and value of the future overlap mental processes and brain regions associated with memory. The research team decided to test the possibility that increasing an individual's ability to remember would decrease the discounting of future events.

"In other words, we asked whether improved memory could result in a greater appreciation of a future reward," said Bickel.

The results of a series of experiments presented a happy answer. Yes. "A change in discounting resulted from reinforced working memory training," the researchers report.

In this study, participants receiving treatment for their stimulant use received either experimental or control memory training. Experimental training consisted of working memory tasks with monetary reinforcement for performance - such as remembering a phone message and memorizing a list of words. Control Training consisted of the same tasks, but with answers provided so there was no memorization required. Experimental participants received monetary rewards for their performance and the control participants received monetary rewards independent of their performance.

The researchers believe the study may be the first to demonstrate that neurocognitive training of working memory can decrease delay discounting.

The research article reports, "These findings support the competing neurobehavioral decision systems hypothesis of addiction (that) decisions are made on the basis of two decision systems. One, referred to as the impulsive decision system, is embodied in the limbic and paralimbic brain regions and is associated with the acquisition of more immediate reinforcers. The other, referred to as the executive system, is embodied in the prefrontal cortex and is associated with planning and deferred outcome. According to this hypothesis, addiction results from a hyperactive impulsive system and a hypoactive executive decision system. - (O)ur observed decrease in the rate of discounting following working memory training is consistent with an increase in relative activation of the executive system."

The researchers conclude, "These changes in executive function are consistent with the notion of neuroplasticity and suggest that at least some of the neurocognitive deficits related to addiction might be reversible."

They suggest future research address the durability of memory training, the ceiling effects of training, and the extent of improvement in treatment outcome.

In the journal's Commentary, Bruce Wexler, of the Yale Department of Psychiatry, suggested the improvement in placing value on a future reward may be connected to the reward rather than working memory. He endorsed treatment strategies that strengthen normally occurring processes -- whether memory or the executive decision system -- rather than simply address symptomatic behavior directly. He wrote, "One goal of future studies will be to build on the valuable foundation provided by Bickel et al. in reporting the benefits of a (cognitive remediation treatment) approach for an addiction disorder. New studies should make explicit the cognitive process they aim to target-whether it is working memory, executive function more broadly, or control over financial reward- and include measures, as did Bickel et al., of the effects of treatment on the putative mediators. Future studies must also demonstrate reduction in the clinically problematic behavior to establish the value of the treatment."