Anatomy of apprehension.

Fear gnaws at the amygdala, an almond-shaped lump of tissue located near the center of the brain. Moreover, the sight of frightened faces selectively sets off neural activity in this structure, indicating that it specializes in tracking signs of threat and danger in the social world, a new investigation finds.

Earlier studies of monkeys and people had shown that damage to the amygdala makes it difficult to learn to fear potentially painful stimuli and to recognize fear in others' faces.

Raymond J. Dolan of the Wellcome Department of Cognitive Neurology in London and his colleagues took positron emission tomography (PET) brain scans of five adults as they viewed photographs showing fearful or happy faces of varying emotional intensity. The left side of the amygdala showed much more activity, as signified by increased blood flow, in response to fear than to happiness. As the fear perceived in the photos grew in intensity, so did neural activity in the amygdala, Dolan's team asserts in the Oct. 31 Nature.