A clearer picture of teenage brain development
Abstract: The study provides evidence of a critical period for neuroplasticity in the frontal cortex during the teenage years, a time when risky behaviors and the risk of mental illness are at their peak.
Source: University of Pittsburgh
In a paper published in Advances in NeurobiologyNeuroscientists at the University of Pittsburgh School of Medicine have described compelling new evidence for a critical period of neuroplasticity in the frontal region of the brain during adolescence, a time when serious mental illnesses such as depression and schizophrenia emerge and when risky behavior peaks.
Using more than twice the resolution of a typical MRI, the researchers discovered age-related changes in the relative balance of inhibitory and excitatory neurotransmitters in the prefrontal cortex—a brain region responsible for cognition, decision-making, short-term memory, and moderating social behavior.
The study expands scientific understanding of critical neuroplasticity during childhood by providing the first evidence of plasticity in the frontal cortex in adolescence.
“The prefrontal cortex is commonly described as the ‘conductor of the brain,'” said senior author Beatriz Luna, Ph.D., professor of psychiatry at Pitt. “Instead of playing one specific instrument, it coordinates between multiple instruments and brain regions to determine a complex function such as cognition or controlling emotions.”
“This work provides biological evidence for what we’ve all suspected about adolescent behavior,” Luna added.
“Adolescence is a time when cognition becomes specialized to support the transition to adulthood and determine the lifelong trajectories of brain development, which can be disrupted, as is the case with mental illness.”
Adolescence is a unique part of development that has puzzled researchers and parents for generations. This period of growth and development, characterized by heightened sensation seeking, which is adaptive to the acquisition of new experiences necessary for brain specialization in adulthood, begins with the onset of puberty and generally levels off by the time individuals turn 18 or a little older.
Brain plasticity in the critical period is driven by a greater excitatory function compared to inhibitory function, which signals that the nervous systems must reorganize to re-establish balance.
As part of the study, scientists looked at the levels of two brain chemicals — glutamate and gamma-aminobutyric acid, or GABA — in the frontal cortex. Glutamate and GABA are abundant in the brain.
Neurons use glutamate to send activation or excitatory signals through their shoots, while GABA is used to dampen them and inhibit brain activation. This balance between excitation and inhibition is crucial to the brain and what brain development aims to achieve.
Unlike previous studies that used less sensitive brain imaging techniques and only looked at glutamate or GABA levels, Luna and her group’s study investigates the balance between these two neurotransmitters by measuring their levels with a higher degree of precision.
Using high-resolution live brain imaging of 144 adolescent and adult participants, the researchers found that the balance between excitatory glutamate and inhibitory GABA increases in adulthood. This increase was primarily due to a significant decrease in glutamate, which approached GABA levels with age.
Together, the findings illuminate critical period plasticity in the brain’s frontal cortex and emphasize that, during adolescence, the dynamic shaping of brain regions that support cognition and cognitive control has important implications for how we understand the biological mechanisms of heightened sensation seeking and other adaptive behaviors that underpin adult brain pathways.
Expanding the understanding of chemical changes in the brain and defining the normative biological mechanisms of brain plasticity is essential to inform the development of therapies targeting mental health disorders.
“It is important to study the fundamental changes in the brain that drive the transition from adolescence to adulthood,” said lead author Maria Perica, a research intern in clinical psychology at Pitt. “Incomplete knowledge of normative brain development limits our understanding of what drives some of the changes we see clinically.”
Additional authors of this study are Finnegan Calabro, Ph.D., Bart Larsen, Ph.D., Will Foran, Ph.D., Victor Yushmanov, Ph.D., and Chan-Hong Moon, Ph.D., all of Pitta; Hoby Hetherington, Ph.D., of the University of Missouri; and Brenden Tervo-Clemmens, Ph.D., of Massachusetts General Hospital and Harvard Medical School.
Financing: This research was supported by the National Institutes of Health (grant MH067924) and the Staunton Farm Foundation.
About this news about neuroplasticity research
Original research: Closed access.
“Development of frontal GABA and glutamate supports excitation/inhibition balance from adolescence to adulthood” Beatriz Luna et al. Advances in Neurobiology
Development of frontal GABA and glutamate supports excitation/inhibition balance from adolescence to adulthood
Postmortem studies in animals and humans provide evidence for changes in gamma-aminobutyric acid (GABA) and glutamate in the prefrontal cortex (PFC) during adolescence, suggesting changes in the balance of excitation and inhibition consistent with critical period plasticity.
However, how GABA and glutamate change during adolescence and how the balance of these inhibitory and excitatory neurotransmitters changes is not well understood in vivo in humans..
High-field magnetic resonance spectroscopy (7 Tesla) was used to investigate age-related changes in GABA/creatine (Cr) and glutamate/Cr balance in several developmentally relevant regions of the frontal cortex in 144 individuals aged 10 to 30 years. .
The results indicated a homogeneous pattern of age-related Glu/Cr reduction across regions, whereas age-related changes in GABA/Cr were heterogeneous, with a mixture of stable and declining age effects.
Importantly, the balance between glutamate/Cr and GABA/Cr in frontal cortex regions increased during adolescence, suggesting the presence of critical period plasticity in the frontal cortex during this important period of development when adult trajectories are established.