African Americans and Caucasians viewing African American faces display
extremely similar changes in the activity of brain structures that respond to
emotional events, a new UCLA study finds.
The changes occur in the amygdala, a region of the brain that serves as an
"alarm" to activate a cascade of other biological systems to protect the body
in times of danger, said Matthew D. Lieberman, assistant professor of
psychology at UCLA and lead author of the study.
The findings will be published May 8 in the online version of Nature
Neuroscience, and later in the print version.
Five out of eight African Americans (63 percent) responded with
significantly more amygdala activity when presented with expressionless
photographs of African Americans than when they were shown expressionless
photographs of Caucasians, Lieberman and his colleagues found. Seven of
11 Caucasians (64 percent) in the study also responded with greater activity
in the amygdala when viewing the African American photographs.
Although a third of participants in each race did not show this effect, no
participant in the study responded with greater amygdala activity to the
Caucasian photographs than to the African American photographs, Lieberman
said.
"We didn't see any differences in amygdala activity between the racial
groups," Lieberman said. "From looking at the amygdala, you couldn't tell if
the scans were from African American or Caucasian participants.
"Many people of either race may not be happy to find out that a part of
their brain involved in responding to potential threats responds more to
African Americans than Caucasians," Lieberman said. "Even people who believe
to their core that they do not have prejudices may still have negative
associations that are not conscious."
Why do African Americans have this amygdala response?
"One theory," Lieberman said, "is that people are likely to pick up the
stereotypes prevalent in a society regardless of whether their family or
community agrees with those stereotypes. Several social psychologists have
found evidence for this view. From an early age, cultural views, media
portrayals and even the body language of authority figures may train our
brains, whether we consciously agree or not."
Previous research has shown that Caucasians show an increased amygdala
response to African American photos to the extent that they hold nonconscious
negative attitudes towards African Americans, Lieberman said.
Co-authors on the study are Johanna Jarcho, a UCLA graduate student in
Lieberman's laboratory; UCLA graduate student Naomi Eisenberger; Susan
Bookheimer, professor of psychiatry and biobehavioral sciences at UCLA's David
Geffen School of Medicine; and Ahmad Hariri, assistant professor of psychiatry
at the University of Pittsburgh School of Medicine and a former UCLA graduate
student.
The researchers also studied whether adding a verbal label (such as
"African American") when viewing African American photos changes the amygdala
response, and found it does.
"When people look at an African American and think of the word 'African
American,' we no longer see the amygdala response," Lieberman said. Instead,
the researchers found changes in a second region of the brain: the right
ventrolateral prefrontal cortex. This region of the brain is located behind
the forehead and eyes, and has been associated with thinking in words about
emotional experiences; it also is associated with inhibiting behavior,
impulses and emotions.
"This region is especially active when you add the verbal label to the
face," Lieberman said. "The people who show the most activity in the
right ventrolateral prefrontal cortex show the least activity in the
amygdala.
"We found that when the right ventrolateral prefrontal cortex gets turned
on, the amygdala does not," he added. "When you engage in verbal labeling,
that partially turns off or disrupts the amygdala response. The right
ventrolateral prefrontal cortex was significantly active only when people were
looking at African Americans and choosing the word 'African American.'"
These results suggest that "thinking about the race of others in words may
regulate some of the threat experienced when confronting unfamiliar or feared
others," Lieberman said. "It is possible this emotional 'benefit' of using
race-related words may have inadvertently contributed to the widespread use of
race-related words and stereotypes."
Lieberman and his colleagues used functional magnetic resonance imaging
(fMRI) to examine brain activity for this study, conducted at UCLA's
Ahmanson-Lovelace Brain Mapping Center.
The research was supported by the National Science Foundation and the
National Institute of Mental Health.
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