Amygdala damage leads to abnormal fear reaction

Normally fear reactions in the brain alert animals and humans to the dangers they are facing, but researchers say they have found a woman with no fear. 

Justin S Feinstein and colleagues at University of Iowa in Iowa City and other universities say their study suggests amygdala plays a pivotal role in triggering a state of fear. 

Amygdala is part of the brain which is involved in memories and emotions including the state of fear. 

The study, reported in the December Current Biology,  profiles  a woman named SM with focal bilateral amygdala lesions. 

She did not have normal fear responses to fear factors that trigger fear in normal people when researchers exposed her to live snakes, spiders, a haunted house, and  emotionally evocative films. 

However, the woman was able to show other basic emotions and experienced the respective feelings. 

Amygdala can be affected by foods such as alcohol. 

One study published in the November 2010 of Neuroimage suggests alcohol may attenuate an individual's response to social threats. 

For this study, Sripada C.S. and colleagues at the University of Michigan in Ann Arbor, MI examined how alcohol affects amygdala reactivity to threatening information in humans. 

The researchers tested 12 healthy social drinkers and found alcohol significantly reduced amygdala reactivity to threat signals or subjects after drinking alcohol were more likely to be fearless when facing threat signals. 

Drinking alcohol is linked to elevated risk of law-breaking.

David Liu and editing by Aimee Keenan-Greene