A new study, published online on December 16 in Current Biology, a Cell Press publication, offers new insight into the emotional life of a unique individual who completely lacks the function of an almond-shaped structure in the brain known as the amygdala. Studies over the last 50 years have shown that the amygdala plays a central role in generating fear reactions in animals from rats to monkeys. Based on the detailed case study of the woman identified only as SM, it now appears that the same is true of humans.
She knows no fear.
To explore this role of the amygdala, Feinstein and his Univeristy of Iowa team observed and recorded SM's responses in a variety of situations that would make most people feel fear. They exposed her to snakes and spiders, took her to one of the world's scariest haunted houses, and had her watch a series of horror films. They also had her fill out questionnaires probing different aspects of fear, from the fear of death to the fear of public speaking. On top of that, SM faithfully recorded her emotions at various times throughout the day while carrying around an electronic diary over a 3-month period. Across all questionnaires, measures, and scenarios, SM failed to experience fear.
That apparent lack of fear mirrored her personal experience, Feinstein said. "In everyday life, SM has encountered numerous traumatic events which have threatened her very existence, and by her report, have caused no fear. Yet, she is able to feel other emotions such as happiness and sadness. Taken together, these findings suggest that the human amygdala is a pivotal area of the brain for triggering a state of fear."
Drugs to suppress the amygdala might help those with post-traumatic stress syndrome. Or perhaps right after a traumatic experience soldiers could be given drugs to disable the amygdala to prevent conditioning to feel severe fear? Her emotional core is immune to the horrors of life.
"This past year, I've been treating veterans returning home from Iraq and Afghanistan who suffer from PTSD. Their lives are marred by fear, and they are oftentimes unable to even leave their home due to the ever-present feeling of danger," Feinstein said. "In striking contrast, the patient in this study is immune to these states of fear and shows no symptoms of post-traumatic stress. The horrors of life are unable to penetrate her emotional core. In essence, traumatic events leave no emotional imprint on her brain."
My theory: the cowardly lion had an over-active amygdala.
|Share |||Randall Parker, 2010 December 16 11:49 PM Brain Emotions|