What happens in the brain when we experience a panic attack?

—Davide Razzoli, Italy

Paul Li, a lecturer of cognitive science at the University of California, Berkeley, explains:

BEFORE GOING onstage to give a presentation, you notice your breathing becomes heavy, your hands tremble and you feel faint. Though frightening, these symptoms are not life-threatening; rather they are indicative of a panic attack.

We know a fair amount about the physiology of a panic attack, but we have only recently started to understand how it affects our brain chemistry. Panic attacks are episodes of intense fear or apprehension. Sufferers often report thinking that they might be dying, choking or going crazy. They may also feel like they are experiencing a heart attack or about to black out. These episodes usually begin abruptly, reach their peak within 10 minutes and end within half an hour.

When people feel stressed, their sympathetic nervous system typically revs up, releasing energy and preparing the body for action. Then the parasympathetic nervous system steps in, and the body stabilizes to a calmer state. If the parasympathetic nervous system is somehow unable to do its job, a person will remain fired up and may experience the heightened arousal characteristic of a panic attack.

Recently researchers have identified certain regions of the brain that become hyperactive during a panic attack. These regions include the amygdala, which is the fear center of the brain, and parts of the midbrain that control a range of functions, including our experience of pain. A study performed by scientists at the Wellcome Trust Center for Neuroimaging at University College London used functional MRI to locate which specific brain regions kick in when a person senses an imminent threat. They found activity in an area of the midbrain called the periaqueductal gray, a region that provokes the body’s defensive responses, such as freezing or running. Dean Mobbs, the lead author on the study, wrote: “When our defense mechanisms malfunction, this may result in an overexaggeration of the threat, leading to increased anxiety and, in extreme cases, panic.”

By identifying brain regions involved in panic attacks, such studies can improve our understanding of anxiety-related disorders and in turn help researchers find better treatments.

Why did the absence of the corpus callosum in Kim Peek’s brain increase his memory capacity?

—A. Goze, via e-mail

Jeannine Stamatakis, instructor at Ohlone College and other colleges in the San Francisco Bay Area, responds:

I MET KIM PEEK when he gave a presentation at Ohlone College in October 2009, just a few weeks before his passing. During the talk, Peek astonished my students by showcasing his remarkable talent for calendar calculations. Just from knowing my students’ birth dates, Peek was able to determine the day of the week they were born and could recall the front-page news that day.

Known as a mega savant or a “Kimputer,” Peek had one of the most impressive memories people have ever seen. Physicians who examined Peek discovered that he had damage to the cerebellum, a brain region that regulates attention and language, as well as emotional

reactions, such as pleasure and fear.

Perhaps most notably, physicians found that Peek had no corpus callosum, the bundle of nerves that connects the brain’s right and left hemispheres. They speculated that the absence of this critical structure allowed Peek’s neurons to make new and unusual connections between his right and left hemispheres. These novel connections most likely explain his abnormal memory capacity.

According to Peek’s father, Peek could memorize every word in the books they read before he was two years old. Peek progressed to reading two pages simultaneously. Although how he did so remains a mystery, some have theorized he read the left page of a book with his left eye and the right page with his right eye.

Peek could soak up material in any subject and became an expert in history, sports trivia, geography and music. He memorized zip codes, area codes and phone books. He could tell if a musician was “off” by a few notes in an orchestra setting—and would even call them on it.

Peek’s unique abilities inspired the character Raymond Babbitt, played by Dustin Hoffman, in the 1988 movie Rain Man. To accurately portray Peek, Hoffman met him and other savants; however, unlike Peek, Babbitt was portrayed as having autism.