September 1, 2000

The ins and outs of facial processing

The human brain devotes some of its most basic structures to recognizing faces and the subtleties of facial expression. Now a study using sophisticated imaging technology has shown that a key part of the brain reacts differently to faces from the person's own racial group than to faces from another racial group. The report from researchers at the MGH, Amherst College, and other institutions appears in the August 2000 issue of NeuroReport.

"One of the most exciting things about this study is how it shows the potential of applying powerful imaging techniques to questions of social psychology," says Scott Rauch, MD, director of Psychiatric Neuroimaging Research at MGH, who is the paper's senior author.

Allen Hart, PhD, chair of the Department of Psychology at Amherst, the paper's first author, adds, "As long as scientists are very careful about how they interpret the results of studies like this, this represents a major new tool to help advance the field."

Located deep within the brain, the amygdala acts as a sort of administrator for the brain, receiving sensory signals and flagging those that need extra attention. Early studies of the amygdala have identified its role in recognizing fear and other strong emotions, and study co-author Paul Whalen, PhD, has theorized that increased activity in the amygdala is a sign of vigilance, a way for the brain to send out a request for more information. Whalen was at the MGH and is now at the University of Wisconsin.

Many amygdala studies have used functional magnetic resonance imaging (fMRI), to measure the amygdala's activity while volunteers viewed photos of faces – usually Caucasian – with a variety of standardized emotional expressions. To examine whether amygdala reaction might differ depending upon whether people are viewing faces from their own race (ingroup) or another race (outgroup), the researchers measured amygdala activity in eight volunteers – four white and four black – as they viewed faces that were neutral in expression and evenly divided among black and white. While amygdala responses to all faces are elevated in an initial set of scans, in a subsequent set of scans there was a reduced response to the ingroup faces only.

Rauch says: "These findings could suggest that people become familiar with elements of ingroup faces more quickly than they do outgroup faces." But the researchers note that more questions need to answered in future studies before any conclusions can be drawn.