We used to think that teens respond differently to the world because of
hormones, or attitude, or because they simply need independence. But when adolescents' brains are studied through magnetic resonance imaging (MRI), we see that they actually work differently than adult brains.
At the McLean Hospital in Belmont, Mass., Deborah Yurgelun-Todd
and a group of researchers have studied how adolescents perceive emotion as
compared to adults. The scientists looked at the brains of 18 children between
the ages of 10 and 18 and compared them to 16 adults using functional magnetic
resonance imaging (fMRI). Both groups were shown pictures of adult faces and asked to
identify the emotion on the faces. Using fMRI, the
researchers could trace what part of the brain responded as
subjects were asked to identify the expression depicted in the picture.
The results surprised the researchers. The adults correctly identified the expression as fear. Yet the teens answered "shocked,
surprised, angry." And the teens and adults used different parts of their brains to process what they were feeling. The teens mostly used the amygdala, a small almond shaped region that
guides instinctual or "gut" reactions, while the adults relied on the frontal
cortex, which governs reason and planning.
As the teens got older, the center of activity shifted more toward the
frontal cortex and away from the cruder response of the amygdala.
Yurgelun-Todd, director of neuropsychology and cognitive neuroimaging at
McLean Hospital believes the study goes partway to understanding why the
teenage years seem so emotionally turbulent. The teens seemed not only to be
misreading the feelings on the adult's face, but they reacted strongly from an
area deep inside the brain. The frontal cortex helped the adults distinguish
fear from shock or surprise. Often called the
executive or CEO of the brain, the frontal cortex gives adults the ability to distinguish a
subtlety of expression: "Was this really fear or was it surprise or shock?"
For the teens, this area wasn't fully operating.
Sarah Spinks is an independent director and producer. She was with the Canadian Broadcasting Corporation for 17 years, where her documentaries won many awards. Spinks' last FRONTLINE documentary, "Making Babies," reported on state-of-the-art infertility treatments.
|When reading emotion, teens (left) rely more on the amygdala, while adults (right) rely more on the frontal cortex.|
Reactions, rather than rational thought, come more from the amygdala, deep in the brain, than the frontal cortex, which led Yurgelun-Todd and other
neuroscientists to suggest that an immature brain leads to impulsivity, or what
researchers dub "risk-taking behavior." Although it was known from animal
studies and brain-injured people that the frontal cortex matures more slowly
than other brain strucures, it has only been with the advent of functional MRI
that researchers have been able to study brain activity in normal children.
The brain scans used in these studies are a valuable tool for researchers.
Never before have scientists been able to develop data banks of normal, healthy
children. Outlining the changes in normal function and development will help
researchers determine the causes of psychiatric disorders that afflict children
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