In what is the first brain imaging study of dread, new research supported by the National Institute on Drug Abuse (NIDA), National Institutes of Health, has shown that people who experience substantial dread about an adverse experience can be biologically distinguished from those who can better tolerate the experience. Understanding how the brains of nonaddicted people guide them in selecting what actions to take when the outcome of a decision is unpleasant lays the foundation for further investigations that can compare how drug abusers' brains make such choices. The study is published in the May 5, 2006 issue of the journal Science.
"Brain imaging technology offers unique insight into the biological mechanisms involved in decision-making, which is invaluable in developing tailored treatment strategies for addiction and drug abuse," says NIH Director Dr. Elias Zerhouni.
"There is substantial evidence that drug abusers place more value on short-term, rather than long-term outcomes," says NIDA Director Dr. Nora D. Volkow. "Past investigations that have looked at how drug abusers make choices have used positive rewards. But this study looked at how people made choices when faced with unpleasant stimuli."
In the study, Dr. Gregory Berns of Emory University School of Medicine and his colleagues used functional magnetic resonance imaging (fMRI) to create images of brain activity in 32 nondrug-abusing participants awaiting brief electrical shocks to their feet. By charting which regions experience increased blood flow over time, fMRI helps scientists understand the relationship between particular types of mental activity and specific areas of the brain.
They observed that activity patterns associated with the dread of waiting involved areas of the brain that govern human pain perception. Specifically, the responses were seen in brain areas that appear to be ruled by attention more than regions associated with fear.
The scientists determined each participant's maximal pain threshold and then presented them with a series of choices from 36 possibilities. For example, each person could elect to receive a shock that was 30 percent of their threshold in 27 seconds or one that was 60 percent in 9 seconds.
"We noted that normal, healthy subjects could be divided into two groups - extreme dreaders, who could not tolerate a delay and preferred an immediate (and stronger) painful stimulus; and mild dreaders, who could tolerate a delay for a milder shock," says Dr. Berns. "We saw that the extreme dreaders could be distinguished from the mild dreaders by virtue of the information captured on the brain scans. The findings suggest that dread derives, in part, from the attention devoted to the expected physical response and is not simply a fear or anxiety reaction."
"Continuing to use drugs despite the expectation of the practice's negative effects is a hallmark of addiction," says Dr. Volkow. "The results of this study form the foundation for future research to determine whether drug abusers exhibit disruption in the brain systems that process the anticipation of unpleasant consequences."