Few events in popular music were as momentous as the Beatles first appearance on the Ed Sullivan Show on February 9, 1964. Paul McCartney recently revisited the Ed Sullivan Theater to appear on the Late Show with David Letterman, and he recounted a story about his early appearances as a young man.
As he waited to go onstage, a stage manager asked McCartney, "Are you nervous?
"No, not really."
"You should be, there are over 70 million people watching."

How can someone be relaxed before such a tremendous occasion, a 3-minute opportunity that could make or break their career? For many of us, it's not easy to keep our composure when we're about to perform. In fact, public speaking is the number one fear of many people, even more frightening than death. Nonetheless, some people seem to be naturals, born performers, so what makes them different? The ability to remain calm could be due to the structure of the brain.

The brain holds a powerful sway over the body. Just thinking about going onstage can produce butterflies in your stomach. The limbic system, an emotional brain region including the amygdala, is closely connected to the autonomic system, which controls your fight-or-flight response; it can make your heart beat faster and your knees go weak. The amygdala, a central brain structure highly active when we're afraid, is also connected to more rational brain regions such as the prefrontal cortex through white matter pathways.

The brain can be divided into two functional categories, gray matter and white matter. Gray matter performs heavy-duty processing, like a computer, but it only functions on a local level. White matter helps distant brain regions communicate by carrying signals over long distances. You could imagine white matter as the telephone lines that transmit conversations between regions of gray matter. The quality and strength of the signal carried by white matter is determined by how thick the lines are and how well they're insulated, which can vary from person to person. For example, research has shown that long-term cocaine abuse may disrupt brain function by deteriorating white matter pathways.

Previous studies have found a pathway between the amygdala and the ventro-medial prefrontal cortex (vmPFC), a brain region that helps process risks, but the significance of that connection was unknown. A recent study by Justin Kim and Paul Whalen at Dartmouth investigated the role that connection strength between those two regions plays in anxiety. Using a magnetic resonance imaging (MRI) technique called fractional anisotropy (FA), which determines white matter integrity, they found people with the lowest levels of anxiety also had the most robust white matter pathways between vmPFC and amygdala.

They also showed the subjects fearful pictures to see if amygdala activation alone predicted anxiety. Interestingly, although the amydgala is active during fear, the people who were more anxious did not have higher levels of amygdala activation. Neither did the people who had lower anxiety have more activation in the vmPFC, which purportedly cools off anxiety. The best predictor of anxiety was the strength of the connection between the two regions. Why might connection strength be more important than the amount of activation in either region alone?

The vmPFC assesses the risk a situation poses and can help decide whether or not you're in an emergency condition. The vmPFC may calm the amygdala to help you feel more in control, but its ability to do so may depend on how well the two regions are wired. If the signal is strong, the vmPFC may shut down the fight-or-flight response and let you make more levelheaded, rational decisions.

People with stronger and heartier white matter pathways may have lower levels of anxiety because they're able to calm down more effectively. This may be important for having the steely nerves it takes to go on stage in front of a live television audience or to speak up in class or in business meetings.

Even if you are someone who gets nervous before making phone calls, there's hope in this finding that may give you pluck. It was formerly believed that the adult brain was static and that after the growth and pruning that takes place when we're children and adolescents, we're stuck with what we've got. What we're finding now is that the brain is constantly in a state of revision. Not only can we develop new neurons, but perhaps more importantly we can also develop new connections or strengthen preexisting connections between neurons.

Because the pathway between the amygdala and the vmPFC is a two-way street, these two regions presumably modulate each other. The amygdala activates when anxiety-producing situations arise, and the vmPFC decides whether or not it is a real emergency or a false alarm. The more exposure you have to nerve-wracking situations, the more you can train your brain to relax, presumably by bolstering the pathway from the vmPFC back to the amygdala. Finally, having a bit of nervous energy may not be a bad thing. By activating the autonomic system, your brain and body will be alert, poised and prepared for action. That way, if all else fails, at least you'll be ready to duck when the tomatoes start flying.


The study was conducted by M. Justin Kim and Paul J. Whalen in the Department of Psychological and Brain Sciences, Dartmouth College, Hanover, New Hampshire.
"The Structural Integrity of an Amygdala-Prefrontal Pathway
Predicts Trait Anxiety" Journal of Neuroscience. September 16, 2009 11614-11618

Thanks to Alice Chi for insights and suggestions.  

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