Brain structure sounds off to fear, anger.

More than 20 years ago, a small clump of tissue called the amygdala was removed from a woman's brain to control her epileptic seizures. While the surgery succeeded in quelling the electric storms in her head, it also drained her of the ability to perceive signs of fear and anger in others' voices, a new study finds.

Prior clinical reports had suggested that the amygdala orchestrates the recognition of fearful and angry facial expressions (SN: 12/17/94, p. 406). The new study suggests that this almond-shaped structure handles various types of sensory information related to social threats, argue neuropsychologist Andrew W. Young of the Medical Research Council Applied Psychology Unit in Cambridge, England, and his colleagues.

"A plausible hypothesis is that impaired recognition of fear and anger after amygdala damage reflects involvement of the amygdala in the appraisal of danger and the emotion of fear," the scientists report in the Jan. 16 Nature. The woman studied by Young's group displayed marked difficulty in understanding vocal intonations used to express emotions, particularly fear and anger. For instance, when listening to a recording of single words with neutral meanings (such as "carpet") spoken with intonations intended to convey any of several emotions, she almost never identified anger or fear. A troublesome number of errors also occurred for happy and sad intonations. Nonverbal expressions of fear and anger, such as growls and screams, also eluded her comprehension, although she usually recognized sounds that signify happiness, sadness, disgust, and surprise.

The woman had no hearing defects and demonstrated a full understanding of the circumstances under which people experience various emotions, the researchers note.

"I'm not surprised by these new findings," says psychiatrist Leslie A. Brothers of the West Los Angeles Veterans Affairs Medical Center. "I suspect the amygdala is important for interpreting all types of signals people use to communicate what they're thinking, not just those concerned with fear and anger."

Psychologist Lawrence F. Cahill of the University of California, Irvine welcomes Young's report. Unlike Brothers, he views the amygdala primarily as a site for interpreting emotions and rendering emotional events into highly memorable forms. A related study, published in the Dec. 1, 1996 Journal of Neuroscience, indicates that parts of the right hemisphere allow for the recognition of negative emotions independently of the amygdala, at least in adults. Of 37 people who had suffered cerebral damage, mainly due to strokes, only those whose injuries involved one of two right-brain areas-one that interprets visual input and one that perceives body states-showed difficulty in recognizing fear and anger in faces. None of these people had amygdala damage, note neuropsychologist Ralph Adolphs of the University of Iowa College of Medicine in Iowa City and his coworkers.