In reality, the tarantula videos had been recorded earlier. But the subjects didn't know that, allowing their brain scans to reveal the way they processed the threats from the tarantulas as the spiders moved closer to, or further away from, their feet.
"When a spider is placed closer, activity increases in the brain's fear areas. These areas are strongly implicated in defensive response as well as panic," Mobbs said. When the tarantulas moved, activity spiked in the parts of the brain involved in "vigilance or tracking threat," he added.
In conjunction with other findings, "this suggests that many parts of the fear system are working in tandem, each evaluating the external threat in different ways," Mobbs said.
What's next? "A goal of future research should be to try and understand which part of the system breaks down [with phobias]," Mobbs said. "If we can understand this, then we can better engage people with phobias and other types of fear."
The subjects in this study didn't have phobias. But in the future, research could enlist phobic people to see if their brains respond differently to the threat, said Joseph LeDoux, a professor of neuroscience at New York University.
To learn more about phobias, try the U.S. National Library of Medicine.
SOURCES: Dean Mobbs, Ph.D., neuroscience researcher, MRC Cognition and Brain Sciences Unit, Cambridge, U.K.; Joseph LeDoux, Ph.D., professor, neuroscience, New York University; Nov. 8-12, 2010, Proceedings of the National Academy of Sciences, online
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