A balancing act in teen brains

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Teens often make choices that confound the adults in their lives. Sometimes they might seem to inhabit a different universe, where consequences are an afterthought in the pursuit of new, exciting experiences. Recent findings from Pitt scientists point to one possible reason for the divide: A critical period of neuroplasticity in the adolescent brain.

As described in a paper published in Progress in Neurobiology, the researchers looked at the balance of two brain chemicals—glutamate and gamma-aminobutyric acid (GABA)—in the prefrontal cortex. Neurons use glutamate to send activation, or excitatory, signals across their branches, while GABA dampens them and inhibits brain activation.

Using high-resolution live brain imaging on 144 participants, the researchers found that as adolescents age toward adulthood, glutamate levels taper off, and the two neurotransmitters come into balance.Luna

The research, supported by the National Institutes of Health and the Staunton Farm Foundation, offers new understanding about adolescents’ heightened sensation-seeking, which allows them to gain the new experiences needed to specialize the brain (that is, engage and solidify its circuitry) in adulthood. But it can also lead to potentially life-threatening, risk-taking behaviors that begin with the onset of puberty. What’s more, major mental illnesses such as depression and schizophrenia often first emerge during this time.

“This paper provides biological evidence for what we have all suspected regarding adolescent behavior,” says senior author Beatriz Luna, a PhD, the Staunton Professor of Pediatrics and Psychiatry and Distinguished Professor of Psychiatry and Psychology at Pitt. “Adolescence is the time when cognition becomes specialized in supporting the transition to adulthood and determining lifetime brain development trajectories.” Yet that development can be derailed, as in the case of mental illness, she adds.

Critical periods of neuroplasticity—when the brain is especially sensitive to changes—involve high excitatory function in relation to inhibitory function, which signals that neural systems must reorganize to regain balance. Scientists have previously identified critical neuroplasticity periods during infancy and childhood, but this study offers the first evidence of profound plasticity in the frontal cortex during adolescence.

“It’s important to study foundational changes in the brain that drive the transition from adolescence to adulthood,” says lead author Maria Perica, a PhD candidate in clinical psychology at Pitt. “Incomplete knowledge about normative brain development limits our understanding of what drives some of the changes we see clinically.”   —Staff reports