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Scaring Those Who Have No Fear

Scientists found a way to cause panic attacks in women with amygdala damage.

By | February 5, 2013

WIKIMEDIA, AMBER RIEDER, JENNA TRAYNOR, AND GEOFFREY B HALLThe almond-sized brain structure called the amygdala has been thought to be essential for experiencing fear. People with amygdala damage may go through life without feeling frightened by spiders, horror films, or even life-threatening trauma. But scientists have found a way to make three women with damaged amygdalae panic, Nature reported.

The researchers, who published their work in Nature Neuroscience on Sunday (February 3), came upon their discovery by surprise. For years, they had been studying a 44-year-old woman with Urbach-Wiethe disease, a genetic disorder that can cause skin problems and hardening of brain tissue. She had not reported feeling fear since childhood. But when the researchers had her breathe air with elevated levels of carbon dioxide gas—which causes no real danger, but can trigger a sensation of suffocation—she unexpectedly panicked.

The scientists then tested a pair of twins with amygdalae wasted by Urbach-Wiethe disease to see whether they would panic when exposed to carbon dioxide-rich air. They, too, experienced unaccustomed panic.

Interestingly, the three women experienced more panic than healthy volunteers, which do not always panic in response to the carbon dioxide test. The results of the experiment indicate that the amygdala is not essential for all fear responses. The researchers say that the amygdala may be more important for responding to outside threats, such as scary animals, and less necessary for processing internal fears, like the sensation of suffocation or a heart attack.

"This study adds to a growing body of work showing that there are different systems for responses to different kinds of threats,” neuroscientist Joseph LeDoux of New York University, who was not involved in the study, told Nature. “There is lots of evidence that the amygdala contributes to threat-evoked responses, but very little evidence that it generates the conscious experience of fear."

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Avatar of: HiddenWays

HiddenWays

Posts: 1

February 5, 2013

It has been argued (A step in the right direction: comment on '5-HT and mechanisms of defence.  Rodgers RJ, J Psychopharmacology 1991) that fear and panic are separate physiological responses, and fear, mediated by the amygdala, inhibits panic.  If so, it is no surprise that people who cannot feel fear are still subject to panic.

Avatar of: James V. Kohl

James V. Kohl

Posts: 194

October 31, 2013

Top-Down Control of Visual Responses to Fear by the Amygdala
Nicholas Furl, Richard N. Henson, Karl J. Friston, and Andrew J. Calder
J. Neurosci. 2013;33 17435-17443
  "Amygdala therefore may control how behaviorally relevant information is visually coded in a context-sensitive fashion."   Will someone please tell me why they think visual input alone (SNAKE!) could code anything in a context-sensitive fashion (SPIDER!) in any species. I've learned nothing about molecular epigenetics that would suggest anything other than classically conditioned responses (MOUSE!) associated with the epigenetic effects of olfactory/pheromonal input in the context of behavioral development that incorporates the amygdala (ANGRY FACE!) as an olfactory processing structure in humans.   "Our study, the first to apply extensive connectivity modeling to fMRI responses to dynamic and static faces, yields a new perspective on how the amygdala controls the visual system and speaks to novel research avenues." http://www.jneurosci.org/content/33/44/17435.abstract   If the amygdala controls the visual system, the fear of snakes is not directly associated with visual input, is it? If the amygdala controls carbon dioxide-associated panic attacks, the link to olfaction is clearer and that link places visual input in a proper heirarchy of biologically based cause and effect in the snake-centric theory of human brain evolution. The movements of snakes are so atypical of anything seen by mammals, that the innate response to threat is due to lack of associations, not prior associations during our evolutionary past.

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