Scientists Use Tarantulas to Explore Human Fear
TUESDAY Nov. 9, 2010 -- An experiment using humans, video footage of tarantulas and brain scans sheds new light on the many ways your mind responds to perceived danger.
"When we encounter fear, multiple systems in the brain are acting to help you survive. These systems are monitoring the movements of the threat, detecting surprises and calculating how close the threat is to you. Basically, your brain is multitasking and evaluating the best possible way to escape the danger," explained study author Dean Mobbs, a neuroscience researcher at MRC Cognition and Brain Sciences Unit in Cambridge in the United Kingdom.
Fear, of course, is a deeply primitive human emotion. "We now know that fear is not in one place in the brain, but is represented in many different areas that are highly interconnected," Mobbs said. "Different types of fear can tap into many of the same parts of the brain's fear network, from fear of taking an exam to fear of meeting a bear in the woods."
But there's more to figure out about how the process works. In the new study, Mobbs and colleagues sought to gain more insight into how the brain handles one kind of fear in particular -- the fear of spiders.
"The U.K. has one of the highest amount of spider phobics in the world. This is despite the fact that we have no deadly spiders in the U.K.," Mobbs explained. "Presumably, we learn from others or the media that spiders are scary, yet because we don't encounter them, we cannot habituate to them. Thus, our fears persist."
Mobbs has a personal motivation, too: "I mainly used spiders because I have a slight fear of them."
In the study, which appears in this week's online edition of the Proceedings of the National Academy of Sciences, researchers placed 20 participants in functional-MRI machines. The subjects watched videos that appeared to show tarantulas being placed near their feet at that exact moment.
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.
Posted: November 2010