Brain scans show the relationship between addiction and dopemine neurotransmitters

New Research About the Teenage Brain

The prevailing theory about teenagers’ brains is that the prefrontal cortex — which is thought to control complex cognitive behavior and planning — isn’t fully developed. But new research out of the University of Pittsburgh is beginning to challenge that premise. The research was presented at the American Association for the Advancement of Science annual meeting in February. Beatriz Luna, PhD, Staunton Professor of Psychiatry and Pediatrics at the Pitt School of Medicine at the University of Pittsburgh, and her team analyzed results from hundreds of brain scans of teenagers. They used a model in which eye movements, or saccades, reveal insight into executive brain function in adolescence. “Our interest is to try to characterize the changes that are occurring in the level of the brain — its structure, its function, and the organization of its networks,” Dr. Luna says. Through their experiments, the team found that the prefrontal cortex in an adolescent’s brain isn’t significantly different than in an adult’s brain, but that it can easily be overruled by heightened motivation centers in the brain.

Looking Inside the Teen Brain

According to Luna, here’s how the research worked: “We ask individuals to come show individuals what tasks we’re going to ask them to do in the scanner before they go into the scanner. Then we take a picture of their brain and ask them to do the tasks they’ve already seen. Using eye-movement tasks, it’s a sneaky way of testing the brain.” When they’re in the scanner, participants are asked to look at a center fixation in a screen and a little light will appear somewhere else in their field of vision. Their task is to not look at the light. “It seems amazingly simple,” Luna says, “However, what we see is that children do it right 50 percent of the time and adolescents 30 percent of the time. Even adults don’t get it right 10 percent of the time, because if you have a psychiatric disorder, you can’t do this.” According to Luna, the results of the testing are indicating that even with the newly gained control that teens get as their brains mature, the area of the brain that looks for extra rewards pulls them towards instant gratification. “This is a robust way of looking at what we call cognitive control in the brain,” she says. “It’s telling us, ‘I understand the instructions and I’m supposed to look away, but I was unable to engage the brain systems that allow me to have executive control and plan behavior. And instead, my more reactive system is the one that dominated and made me look at the light.’” Luna says that these experiments show that, while the prefrontal cortex is maturing in adolescence, what isn’t quite developed there yet are the systems that support reward processing and motivation. “In the old model, you identify an individual not good at planning and also driven by reactive motivational processes,” she says. “What we find is that the subjects are feeling, ‘I have this prefrontal cortex and I can plan. I don’t need to ask my mom or dad for things and I can figure it out myself.’ And the mechanism that drives kids to go away from safety and their home is that they’ll get a surge of reward processing to motivate them. It’s actually adaptive and a good thing.” Luna says her studies might help experts know how to intervene earlier in the lives of kids who may be at risk for developing problems during adolescence. “We know that across societies and species that adolescence is a period of increased sensation-seeking that can lead to risk taking, which increases mortality rate,” she says. “During this period, we also see the first signs of mental illnesses such as schizophrenia, depression and eating disorders. All of these have a neurological basis, so if we know the brain is changing, we may be able to do something earlier to help.”

The Take-Home Message for Parents and Teens

Johanna Jarcho, PhD, a postdoctoral fellow at the National Institutes of Mental Health, specializes in affective neuroscience, and has thought a lot about the take-home message from this imaging research. “I think it shows a nuanced relationship in adolescents between reward sensitivity and brain function,” she says. “In other words, adolescents have all of the skills to make the right decisions and to identify when things are risky. They just don’t.” While Dr. Jarcho says we’re still far from understanding all of this concretely, the study underscores several important things. “There are many approaches for parents when looking at teen behavior,” she says. “It isn’t one-size-fits-all. The first step is to know your kid. And the message for kids is to know your environment — to look for cues that might make you stop before you make a decision and realize that you have an active role in decision-making.” The basic message from Jarcho is that it’s important for kids to stop and think and not just “go with it.” She believes this study and others shows what adolescents have the intrinsic motivation to do, but this doesn’t also pan out in reality. “I think that being able to try to shift what is salient in the environment is very important in adolescents, to frame it by asking, ‘If I make this decision, what is it that I might be losing?’” she says. “And when you try to avoid losing, you make better decisions. This involves activating cognitive control to avoid a loss situation. And in terms of taking drugs and other risky behaviors, sometimes it’s just easier to put your hand out than to think about what you might lose.”

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