July 3, 2003

Response to new faces varies by temperament

A key area in the brains of people who displayed an inhibited temperament as toddlers shows a greater response to new faces than does the same area in adults who were uninhibited early in life, according to an MGH report. The imaging studies of the amygdala — a part of the brain that responds to events requiring extra vigilance — appear in the June 20 issue of Science.

"Our findings both support the theory that differences in temperament are related to differences in amygdala function, something earlier technology could not prove, and show that the footprint of temperamental differences observed when people are younger persists and can be measured when they get older," says Carl Schwartz, MD, director of the developmental psychopathology lab in the MGH Psychiatric Neuroscience Program, the paper's first author.

Temperament refers to a stable emotional and behavioral profile that is observed in infancy and partially controlled by genetic factors. One temperamental measure relates to a child's typical response to unfamiliar people, objects and situations and is described with terms such as shyness versus sociability, caution versus boldness, or withdrawal versus approach.

The study participants were 22 young adults who had participated as children in studies of temperament by Jerome Kagan, PhD, professor of Psychology at Harvard, a co-author of the study.Thirteen had been determined to be inhibited as infants, and nine were categorized as uninhibited. In the current study, functional MR images were taken while participants viewed a random series of six faces that were presented several times. They then viewed a larger number of faces, some of which were totally new and some that were repeated from the first phase.

While some increase in amygdala response to strange faces is normal, the inhibited participants showed a significantly greater response to the unfamiliar faces than did the uninhibited participants. "It's been theorized that the behavioral differences that characterize inhibited and uninhibited children may relate to the amygdala's response to novelty, and our study supports that concept," says Schwartz. The report's other authors are Scott Rauch, MD, MGH director of psychiatric neuroimaging; Christopher Wright, MD, and Lisa Shin, PhD.