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May 12, 2006
The Neurobiology of Dread
Everyone has to make decisions involving potential gains and losses. It's not always just a rational choice of what we think will bring the better outcome, though. When the outcome's delayed, the feeling we call dread can make a choice considerably more complex. A new study supported by NIH's National Institute on Drug Abuse (NIDA) shows that people who experience substantial dread about an unpleasant experience can be biologically distinguished from those who don't dread it as much. Understanding how people make choices when faced with unpleasant outcomes may yield insights into how to develop ways to counter behaviors that have harmful effects such as drug abuse.
Dr. Gregory Berns of Emory University and his colleagues used functional magnetic resonance imaging (fMRI) to create images of brain activity in 32 people as they waited to receive brief electrical shocks to their feet. By charting which brain 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.
The scientists first found each participant's maximal pain threshold and then presented them with a series of choices about shock intensity and delay — for example, a shock that was 30% of their threshold in 27 seconds or one that was 60% in 9 seconds. The tests were done while the participants were in an fMRI scanning machine, and their choices were compared to their brain scan results The findings were published in the May 5, 2006 issue of the journal Science.
Overall, participants generally chose a shorter delay when the shocks were identical. The researchers found, however, that the participants fell into two groups: extreme dreaders who couldn't tolerate a delay and preferred an immediate shock, even if it was stronger; and mild dreaders, who could tolerate a delay for a milder shock. The greatest difference in brain activity patterns between the two groups was in a region of the brain associated with attention. This suggests that it's not general fear or anxiety that's creating a heightened sense of dread; rather, it's increased attention toward the location of the impending shock.
This research may eventually lead to better pain management strategies. It also raises the question of whether drug or alcohol abusers might anticipate unpleasant consequences differently than others. "Continuing to use drugs despite the expectation of the practice's negative effects is a hallmark of addiction," according to NIDA Director Dr. Nora D. Volkow." This work may eventually shed light on how drug user's anticipation of pain or discomfort can affect the choices they make.