Neuroimaging Studies Offer a New Look at the Teen Brain

Why do teenagers often seem to be a different, even an alien species separate from adults? It's their brain, said Jay Giedd. "It is different from the brain of a child, different from the brain of an adult, but those differences have many upsides."

"All social mammals have increased risk taking, sensation seeking, and move away from their parents to their peers" at adolescence. Giedd's neuroimaging research at the National Institute of Mental Health (NIMH) has helped advance our understanding of those processes.


Jay Giedd [Credit: Bob Roehr]
 

Rebellious separation "is exquisitely forged by the forces of our evolutionary history," perhaps to facilitate separation from the natal family and reduce inbreeding, he explained at a 12 June forum sponsored by AAAS and the Dana Foundation, a leading funder of brain research.

The human brain is plastic and is in the process of remodeling for a very long portion of life, to about age 25. "The brain doesn't mature by getting bigger," Giedd said. "It matures by becoming more connected within itself and more specialized." It trades off a loss in plasticity for faster and more efficient internal processing.

Giedd believes this extended period of brain plasticity and maturation is particularly important today "because there has been a revolution — and I don't use that term loosely" with the advent of digital technology and the Internet. "The way we learn, play, and interact has changed more in the last 15 years," than at any other time in human history, he said.

The scope and depth of information available today through a simple Google search, for example, would have taken weeks if not months to assemble a generation ago. "Adolescents are old enough to master these technologies but young enough to embrace the change," Giedd said.

NIMH is conducting a longitudinal study using brain imaging, neuropsychological and biological markers to better understand the developmental process by assessing more than 3000 teen and young adult participants every two years.

From puberty through the late twenties there is a change in the balance between the brain's prefrontal region involved in long-term thinking and the limbic region that controls more basic body functions. "The part of the brain involved in long-range planning and decision making is the last to mature," Giedd said. It is the change in this balance within the brain, which lasts about a decade, "that accounts for much of what we see in adolescents."


Elaine Walker (top) and Elizabeth Albro (bottom) [Bob Roehr]

Elaine Walker is professor of psychology and neuroscience at Emory University and a researcher with the North American Prodome Longitudinal Study (NAPLS). It seeks to identify early markers for persons at risk of developing psychotic disorders, as well as better understanding of both neurobiological vulnerabilities to the disorders and factors that might trigger their development.

Psychotic disorders occur in 1-2 percent of the population, across cultures, she said. Onset commonly is in late adolescence and early adulthood, when people are learning and gaining social skills. Deficits are associated with low educational and occupational attainment; social withdrawal and limited social networks; low rate of marriage and reduced fertility, especially among males; and lack of insight.

A retrospective study of childhood home movies of patients revealed that long before the onset of any psychiatric disorder, there were subtle abnormalities in posture, movement, and emotional expression such as a disconnect from the surrounding social environment, according to Walker.

Studies of identical twins, where one develops psychosis but the other does not, suggest that environmental factors can generate changes in gene expression that lead to the disease. Walker said a cascade of molecular signals in response to stress likely also plays a significant role in the emergence of psychosis. "When we compare individuals at risk to develop psychosis and their brain changes over time, to those who do not develop psychosis, what we find is much more pronounced loss of brain matter."

"This is before the onset of psychosis ... It is like a normal adolescent developmental trajectory that has been amplified over time," she said. "The higher the cortisol [stress hormone] levels, the lower the brain volume."

The National Center for Education Research at the U.S. Department of Education is focusing on how recent findings in cognitive science and brain development can be exploited to improve teaching and learning among adolescents, said the Center's Associate Commissioner Elizabeth Albro.

The biological transition of adolescence has a parallel in the traditional educational structure as the student moves from having a single teacher in a fixed location to multiple teachers in various locations throughout a generally larger building. Students take on greater responsibility for more aspects of their own education and some schools are teaching skills to help develop the academic and growth mindsets that are associated with success in school.

"With new advances in neuroscience, we are able to ‘see into' a student's mind as they are learning, remembering, and actively solving problems," Albro noted. "We can observe different patterns of activation and different processing routes associated with learning different content, and different learners."

One example Albro cited was a comparison of neurofeedback, which uses the visual display of an electroencephalograph to help a person better understand and control their concentration and activity, and attention training in children with ADHD. The study showed that neurofeedback generated improved attention outcomes among the students.

Recent advances made in understanding the biology of the adolescent brain enthralled all of the forum participants. "We have a lot more leverage for intervening to prevent the onset of psychosis than we have ever known before," Walker said. "There are many potential avenues for leveraging interventions."