Venturing inside the teenage brain

If you’ve ever tried to warn teenagers of the consequences of risky behavior — only to have them sigh and roll their eyes — don’t blame them.

Blame their brain anatomy.

Sociologists and psychologists have long known that teen brains are predisposed to downplay risk, act impulsively and be undaunted by the threat of punishment. But now scientists are beginning to understand why.

"I think teenage behavior is probably the most misunderstood of any age group — not only by parents but by teenagers themselves," says Pradeep Bhide, a Florida State University College of Medicine neuroscientist and director of the Center for Brain Repair.

"It’s a critical time in life, and a very stressful one, when they are going through so many changes at the same time that their brains are changing. The teen years are actually a very busy time for brain development."

During the past year, Bhide brought together some of the world’s foremost brain researchers in a quest to explain why teenagers — and male teens in particular — often behave erratically. He and two Cornell University colleagues examined 20 of the leading research projects from brain experts around the world and recently published their findings in a special volume of the scientific journal Developmental Neuroscience.

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Brain structure could predict risky behavior

Some people avoid risks at all costs, while others will put their wealth, health, and safety at risk without a thought. Researchers at Yale School of Medicine have found that the volume of the parietal cortex in the brain could predict where people fall on the risk-taking spectrum.

Led by Ifat Levy, assistant professor in comparative medicine and neurobiology at Yale School of Medicine, the team found that those with larger volume in a particular part of the parietal cortex were willing to take more risks than those with less volume in this part of the brain. The findings are published in the Sept. 10 issue of the Journal of Neuroscience.

Although several cognitive and personality traits are reflected in brain structure, there has been little research linking brain structure to economic preferences. Levy and her colleagues sought to examine this question in their study.

Study participants included young adult men and women from the northeastern United States. Participants made a series of choices between monetary lotteries that varied in their degree of risk, and the research team conducted standard anatomical MRI brain scans. The results were first obtained in a group of 28 participants, and then confirmed in a second, independent, group of 33 participants.

“Based on our findings, we could, in principle, use millions of existing medical brains scans to assess risk attitudes in populations,” said Levy. “It could also help us explain differences in risk attitudes based in part on structural brain differences.”

Levy cautions that the results do not speak to causality. “We don’t know if structural changes lead to behavioral changes or vice-versa,” she said.

Levy and her team had previously shown that risk aversion increases as people age, and we scientists also know that the cortex thins substantially with age. “It could be that this thinning explains the behavioral changes; we are now testing that possibility,” said Levy, who also notes that more studies in wider populations are needed.

Brain Scans Show We Take Risks Because We Can’t Stop Ourselves

A new study correlating brain activity with how people make decisions suggests that when individuals engage in risky behavior, such as drunk driving or unsafe sex, it’s probably not because their brains’ desire systems are too active, but because their self-control systems are not active enough.

This might have implications for how health experts treat mental illness and addiction or how the legal system assesses a criminal’s likelihood of committing another crime.

Researchers from The University of Texas at Austin, UCLA and elsewhere analyzed data from 108 subjects who sat in a magnetic resonance imaging (MRI) scanner — a machine that allows researchers to pinpoint brain activity in vivid, three-dimensional images — while playing a video game that simulates risk-taking.

The researchers used specialized software to look for patterns of activity across the whole brain that preceded a person’s making a risky choice or a safe choice in one set of subjects. Then they asked the software to predict what other subjects would choose during the game based solely on their brain activity. The software accurately predicted people’s choices 71 percent of the time.

“These patterns are reliable enough that not only can we predict what will happen in an additional test on the same person, but on people we haven’t seen before,” said Russell Poldrack, director of UT Austin’s Imaging Research Center and professor of psychology and neuroscience.

When the researchers trained their software on much smaller regions of the brain, they found that just analyzing the regions typically involved in executive functions such as control, working memory and attention was enough to predict a person’s future choices. Therefore, the researchers concluded, when we make risky choices, it is primarily because of the failure of our control systems to stop us.

“We all have these desires, but whether we act on them is a function of control,” said Sarah Helfinstein, a postdoctoral researcher at UT Austin and lead author of the study that appears online this week in the journal Proceedings of the National Academy of Sciences.

Helfinstein said that additional research could focus on how external factors, such as peer pressure, lack of sleep or hunger, weaken the activity of our brains’ control systems when we contemplate risky decisions.

“If we can figure out the factors in the world that influence the brain, we can draw conclusions about what actions are best at helping people resist risks,” said Helfinstein.

To simulate features of real-world risk-taking, the researchers used a video game called the Balloon Analogue Risk Task (BART) that past research has shown correlates well with self-reported risk-taking such as drug and alcohol use, smoking, gambling, driving without a seatbelt, stealing and engaging in unprotected sex.

While playing the BART, the subject sees a balloon on the screen and is asked to make either a risky choice (inflate the balloon a little and earn a few cents) or a safe choice (stop the round and “cash out,” keeping whatever money was earned up to that point). Sometimes inflating the balloon causes it to burst and the player loses all the cash earned from that round. After each successful balloon inflation, the game continues with the chance of earning another standard-sized reward or losing an increasingly large amount. Many health-relevant risky decisions share this same structure, such as when deciding how many alcoholic beverages to drink before driving home or how much one can experiment with drugs or cigarettes before developing an addiction.

The data for this study came from the Consortium for Neuropsychiatric Phenomics at UCLA, which recruited adults from the Los Angeles area for researchers to examine differences in response inhibition and working memory between healthy adults and patients diagnosed with bipolar disorder, schizophrenia, or adult attention deficit hyperactivity disorder (ADHD). Only data collected from healthy participants were included in the present analyses.

Going with Your Gut

Decision-making is an inevitable part of the human experience, and one of the most mysterious. For centuries, scientists have studied how we go about the difficult task of choosing A or B, left or right, North or South — and how both instinct and intellect figure into the process. Now new research indicates that the old truism “look before you leap” may be less true than previously thought.

In a behavioral experiment, Prof. Marius Usher of Tel Aviv University’s School of Psychological Sciences and his fellow researchers found that intuition was a surprisingly powerful and accurate tool. When forced to choose between two options based on instinct alone, the participants made the right call up to 90 percent of the time.

The results of their study were recently published in the journal PNAS.