Understanding Adolescents a Matter of Inconsistent Brain Development

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Understanding Adolescents a Matter of Inconsistent Brain Development


Jim Windell


          Most of us might wish to go back to ourselves as a 20-something or a 30-something, but hardly anyone wants to go back to their teenage years.

          There was generally so much going on during adolescence that we usually remember it as an awkward, gawky stage of life when we were a tsunami of emotions and that those emotions were as unpredictable as Michigan weather. One minute we were mature and clear thinking; the next we were crying bucketloads of tears. One week we were deeply in love with some pimply-faced peer; the next week we were contemplating never, ever leaving our bedroom.

          If our parents put up with us – God only knows how! – they certainly didn’t understand us. And we didn’t understand ourselves either. But recently a research neuroscientist from Tufts University says she can explain what’s going on with teenagers.

          Ayesha Sengupta, research assistant professor of neuroscience at Tufts University School of Medicine, says there are three areas of development that must be looked at in order to understand adolescents. Those areas are brain development order, brain chemistry and synaptic pruning and environmental maps.

          In terms of brain development, Dr. Sengupta says that the most complex section of the brain, the prefrontal cortical structures, which manages higher order thinking processes and executive functioning, is the last structures in the brain to mature. On the other hand, the amygdala, along with other structures in the temporal lobe of the brain, are more in charge during adolescence because they develop earlier. These sections of the brain trigger emotions and immediate responses to stimuli. 

          During adolescence, teens are more likely to react impulsively because subcortical structures such as the amygdala have matured while the prefrontal cortex is still developing. The connections between the frontal cortex and the amygdala and related regions of the brain also are not yet fully formed.

          As for the brain chemistry, Sengupta and other scientists theorize that adolescence is a time when both brain structural and chemical development is incomplete, leading to less inhibition and more intense emotions. Two neurotransmitters – GABA and glutamate – are the primary chemical messengers of signals between nerve cells in the brain. Other neural signaling chemicals, including serotonin, dopamine, norepinephrine, acetylcholine, and hormones also exert changes in brain activity and can modulate the effects of GABA and glutamate as well. 

          “One hypothesis is that there is less GABA, which is an inhibitory transmitter, in the adolescent brain,” Sengupta says. “We also believe there are different levels or functions of the modulating neurotransmitters in the adolescent brain than the adult brain.”

          Sengupta’s own research looks at communications in the brain’s amygdala and the prefrontal cortex, examining the role of glutamate and how it may be modulated by dopamine and serotonin. “One thing we see across species in adolescence is that when an adolescent learns a simple fear memory – for example, in rodents we test the effects of learning and unlearning the association of a tone paired with a negative stimulus – it’s much harder to extinguish that fear than if it is learned as children or adults,” she says.

          Sengupta’s work is focused on fear and reward learning, and why such emotional learnings are less easy to extinguish in adolescence. She’s examining what happens when positive and negative stimuli are presented together in the same environment to compete for decision making outputs in adolescence.

          When it comes to synaptic pruning and environmental maps, cell-to-cell communication in the brain at the level of individual synapses is also under development in the teen years. In the previously mentioned fear extinction studies, adult rodents demonstrating a greater ability to change than adolescents correlates with something in their synaptic plasticity, or the ability of neurons to modify their connections, differently in adult brains than in teen brains.

          “During adolescence, we also see something called synaptic pruning, where the brain removes synapses it doesn’t need,” Sengupta explains. “This could be particularly relevant since adolescence is a period characterized by new experiences, novelty seeking, learning what the effects of things in your environment will be, and navigating the world more independently.”

          The emotional pressures social media places on teens are also far greater than those experienced by prior generations, and so they experience them far more intensely. Sensation seeking and novelty seeking may occur more in adolescents who are learning their limits without having the regulating effects of a more developed prefrontal cortex or brain chemistry, she adds. “Everything feels more in adolescents. Therefore, it is more memorable, and makes adolescents more vulnerable to its effects.”

          Part of an adolescent’s neurological makeup – such as a predisposition to anxiety or certain mental illnesses – will be inherited. Many of these illnesses first manifest themselves in adolescence.

          “Some mouse models of human genetic traits demonstrate that inherited anxious behaviors are already apparent at adolescence, such as reluctance to explore, and freezing behaviors when faced with negative stimuli,” Sengupta says. 

          Learned fearfulness also occurs throughout life. But experiences are felt more deeply and shaped more intensely in adolescents and seem to be less likely to be “unlearned” than if those experiences occur as children or adults, she adds. 

          “Adolescents are learning their limits while their executive functioning, brain chemistry, and synaptic connections are in flux,” Sengupta says. “This impressionable window of new, salient experiences may be why we see more auto accidents, eating disorders, and suicides during this time-period.” 

          While we hope that most teenagers make it to adulthood without major problems, families, schools, and increasingly the courts, are recognizing that “adolescence is a vulnerable period of brain development,” Dr. Sengupta concludes. 

          To read the article from which this blog was adapted, go to:

Rafferty, J. (2024). Teen behavior, explained by neuroscientist. Tufts Now. Available at: https://now.tufts.edu/2024/04/01/teen-behavior-explained-neuroscientist


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