An alternate pathway to panic

Very interesting article by James Gorman in the NY Times:

In the past few years, scientists have learned a lot about fear from a woman who could not experience it. A rare illness had damaged a part of her brain known as the amygdala and left her eerily unafraid.

Both in experiments and in life, the woman, known as SM, showed no fear of scary movies, snakes, spiders, or very real domestic assaults, death threats and robberies at knife and gunpoint.

Although she lived in an area “replete with crime, drugs, and danger,” according to an earlier study, without a functioning amygdala, an evolutionarily ancient part of the brain long known to process fear, nothing scared her.

But recently SM had a panic attack. And the simple fact that she was able to know fear without a working amygdala, experts say, illuminates some of the brain’s most fundamental processes and may have practical value in the study of panic attacks.

SM’s moments of fear occurred during an experiment that involved inhaling carbon dioxide through a mask in amounts that are not harmful but create a momentary feeling of suffocation. Not only SM, but two other women, identified as AM and BG, identical twins with amygdala damage similar to SM’s, showed all the physical symptoms of panic, and reported that, to their surprise, they felt intense fear.

The researchers, who report on the experiment in the current issue of Nature Neuroscience, had hypothesized that SM would not panic. John A. Wemmie, a neuroscientist at the University of Iowa and the senior author of the paper, said, “We saw the exact opposite.”

Antonio Damasio, of the University of Southern California, who had worked with SM and some of the researchers involved in this study on previous papers, but did not participate in this research, said he was delighted with the results, because it confirmed his own thinking that while the amygdala was central to fear generated by external threats, there was a different brain path that produced the feeling of fear generated by internal bodily experiences like a heart attack. This idea was put forth in a 2011 paper about SM on which he was a co-author. . .

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