recognizing

The woman who knows no fear
17 Dec 94

                                 A PATIENT who cannot read fear on other people's faces has given
                                 researchers a valuable clue to how the human brain processes
                                 emotions. Her confusion shows for the first time that the brain
                                 processes fear and mixed emotions through a different pathway from
                                 those used to process other feelings.

                                 The woman, known as S. M., has a rare disease which has damaged
                                 the amygdala region of her brain. She also has problems perceiving
                                 other "negative" emotions, such as anger and surprise, if expressed at
                                 the same time.

                                 The amygdala is an almond-shaped structure at a crossroads in the
                                 brain's circuitry: it links the cortex, which is responsible for conscious
                                 thought, with regions of the brain that control the body's emotional
                                 responses. Scientists knew that the amygdala helps regulate
                                 reactions associated with strong emotion - such as quickened heart
                                 rate and sweating. But what exactly does it do?

                                 Brain researchers determine the function of a part of the brain by
                                 studying people whose brains are damaged in that region. But patients
                                 with damage to the amygdala alone are very unusual, according to
                                 Antonio Damasio of the University of Iowa, who led the team that
                                 made the new discovery.

                                 S. M. first turned up at a hospital suffering from epilepsy. Later, when
                                 her doctors looked for the root of the problem using magnetic
                                 resonance imaging, they found that her amygdala was destroyed.
                                 This was the result of Urbach-Wiethe disease, which deposits calcium
                                 in the amygdala. With S. M.'s consent, the Iowa researchers
                                 subjected her to a battery of psychological tests devised by
                                 Damasio's colleague Ralph Adolphs, asking her to say what emotions
                                 were being expressed by the people pictured in a series of
                                 photographs.

                                 S. M. failed what Damasio calls "the Doris Day test". "When we
                                 showed her a film clip of Doris Day screaming, she asked, `What is
                                 she doing?'," he says. In fact, S. M. was baffled by any picture
                                 showing a fearful expression. She also had problems deciphering
                                 mixtures of negative emotions, such as anger and surprise. By
                                 contrast, she had no difficulty with "positive" emotions such as
                                 happiness. She was also perfectly able to recognise familiar faces
                                 (Nature, vol 376, p 669).

                                 These results, says Damasio, indicate that the amygdala has a
                                 pivotal role in linking frightening signals from the environment with the
                                 body's fear responses. Fear is universally important for survival in
                                 animals, Damasio notes, so it is reasonable that a special brain system
                                 has evolved to deal with it. The amygdala also seems to help us
                                 respond correctly to complex mixtures of negative emotions expressed
                                 by other people. Because she often fails to recognise criticism or
                                 aggression, S.M. has difficulty interacting socially.

                                 Positive emotions seem to be processed in another region of the brain.
                                 Just where is a mystery. "We've never seen a patient who can't
                                 recognise a happy face," says Adolphs.

                                 JENNIFER ALTMAN
                                  From New Scientist magazine, vol 144 issue 1956, 17/12/1994, page
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