Teenage Kicks: Understanding risky behaviour in adolescence
Our last two blogs have explored some of the amazing changes that occur in the brain during infancy and childhood. However, development does not stop there! While the most dramatic structural changes in the brain have already taken place, our brains continue to develop throughout our teenage years and into adulthood. 1 Adolescence is also marked by substantial neurodevelopment and is widely considered a peak period for neural reorganisation. 2 Teenagers have long-been infamised for their risky behaviour, but have you ever stopped to wonder: Why do teens engage in risky behaviours?
Brain Maturation
It was previously believed that once an individual had gone through puberty and physical growth had come to an end, brain development was complete. However MRI studies have shown that though the brain does not change in size much from the ages of 5 years to 20 years, the connectivity between regions does change. 3 Important brain networks mature during adolescence, as the integrity of white matter tracts - the bundles of myelinated axons discussed in our second blog post - improves and task-related patterns of neural activity change.4 Think of your brain as the internet. All the websites in your brain are set up, but your internet connection is poor during adolescence. This connection improves with age - as your brain matures.
As the volume of grey matter decreases with age, white matter increases. This facilitates faster, more efficient sharing of information between regions.
Copyright (2004) National Academy of Sciences 5
How do teenagers think?
You may have heard of the notion that teenagers ‘think with their feelings’. Well, it is not entirely untrue! The prefrontal cortex, responsible for planning, decision making and self-regulation (see our previous blog post for more details!), is one of the last brain areas to mature. The part of the brain that is responsible for emotional responses - the amygdala - develops much quicker! The prefrontal cortex is the hub of rationality, responding to situations with good judgement and consideration of the consequences of actions. This part of the brain that regulates behaviour in adulthood is not yet mature enough to exert control over teenage impulses. The actions of teenagers are guided by the emotional focal point that is the amygdala, as opposed to the logical prefrontal cortex.
Image Credit: Brain Made Simple
One fMRI study highlighted that adults and adolescents activate different brain regions during an emotion recognition task. 6 While adults correctly recognised a face as being fearful, teens described the face as ‘shocked’, ‘surprised’ and ‘angry’. Researchers found that adults used their prefrontal cortex to complete the task, while teens used their amygdala. To put it simply, teenagers process information differently to adults.
Why engage in risky behaviour?
Research has suggested that adolescents either demonstrate a decreased sensitivity to potential negative outcomes or an increased sensitivity to potential positive outcomes, while some researchers have suggested that teenagers may be ‘hard-wired’ to engage in risky behaviour. 7 The latter suggestion was supported by Cohen and colleagues’ research, requiring 8 to 30 year olds to categorise images as quickly as possible, in exchange for a reward. 8 Participants were offered either a small (5c) or large (25c) reward for correctly categorising specific images. Adolescents were significantly more likely to respond quicker when faced with the large reward, in spite of the increased risk of an incorrect response. Researchers discovered that teenagers released the greatest amount of dopamine - a neural chemical that is associated with pleasure - after receiving a reward. As dopamine motivates the brain to seek rewards, researchers suggested that teens were more willing to take risks to experience rewards. In other words, teenage (risky) behaviour is motivated by a desire to obtain positive outcomes.
However such positive outcomes or ‘rewards’ need not necessarily be physical! Chein et al. reported that teenagers engaged in riskier driving when in the company of their peers in a simulated driving task.9 Again, fMRI showed that adolescents activated reward-related brain regions during this activity. This heightened sensitivity to the potential social rewards associated with risky behaviour has been linked to the increased binge drinking, smoking, violent and criminal behaviour displayed by adolescents.10 As our previous blogs have explained, the way in which infants and children interact with the world around them can have a huge impact on their development. Environmental factors continue to significantly influence how adolescents behave and develop throughout their teenage years - and for many years more!
Come back soon for the final instalment of our ‘Journey Through Your Brain’ blog series, and while you are here, have a scroll through our brand-new website! You can also keep up to date on all the latest from the lab on our Twitter and Facebook pages.
References
Whitford, T. J., Rennie, C. J., Grieve, S. M., Clark, C. R., Gordon, E., & Williams, L. M. (2007). Brain maturation in adolescence: concurrent changes in neuroanatomy and neurophysiology. Human Brain Mapping, 28(3), 228-237. https://onlinelibrary.wiley.com/doi/full/10.1002/hbm.20273
Sisk, C. L., & Foster, D. L. (2004). The neural basis of puberty and adolescence. Nature Neuroscience, 7(10), 1040-1047. https://www.nature.com/articles/nn1326
Lichenstein, S. D., Verstynen, T., & Forbes, E. E. (2016). Adolescent brain development and depression: a case for the importance of connectivity of the anterior cingulate cortex. Neuroscience & Biobehavioral Reviews, 70, 271-287. https://www.sciencedirect.com/science/article/pii/S0149763416301348?casa_token=ZgQDG51SAo4AAAAA:DhkQQZFQPQtA5Wwl0_l4xUt4nPM8UoyPq4915zsMI-Dge9FaeH9dFuPC1zFyNlTd2RIwvB-k
Luna, B., Marek, S., Larsen, B., Tervo-Clemmens, B., & Chahal, R. (2015). An integrative model of the maturation of cognitive control. Annual Review of Neuroscience, 38, 151-170. https://www.annualreviews.org/doi/abs/10.1146/annurev-neuro-071714-034054
Gogtay, N., Giedd, J. N., Lusk, L., Hayashi, K. M., Greenstein, D., Vaituzis, A. C., ... & Rapoport, J. L. (2004). Dynamic mapping of human cortical development during childhood through early adulthood. Proceedings of the National Academy of Sciences, 101(21), 8174-8179. https://www.pnas.org/content/101/21/8174.short
Baird, A. A., Gruber, S. A., Fein, D. A., Maas, L. C., Steingard, R. J., Renshaw, P. F., ... & Yurgelun-Todd, D. A. (1999). Functional magnetic resonance imaging of facial affect recognition in children and adolescents. Journal of the American Academy of Child & Adolescent Psychiatry, 17(2), 143-155. https://psycnet.apa.org/record/1999-00773-018
Casey, B. J., Getz, S., & Galvan, A. (2008). The adolescent brain. Developmental Review, 28(1), 62-77. https://www.sciencedirect.com/science/article/pii/S0273229707000494?casa_token=cjiFr8ppgc4AAAAA:Vk2lfdIzRHxLnOIHvFLDq4wyZodY4Iqkb3nipr0JV5Z0Zf19-zGrZGoJeoEkk1URsA0MTLxL
Cohen, J. R., Asarnow, R. F., Sabb, F. W., Bilder, R. M., Bookheimer, S. Y., Knowlton, B. J., & Poldrack, R. A. (2010). A unique adolescent response to reward prediction errors. Nature Neuroscience, 13(6), 669. https://www.nature.com/articles/nn.2558
Chein, J., Albert, D., O’Brien, L., Uckert, K., & Steinberg, L. (2011). Peers increase adolescent risk taking by enhancing activity in the brain’s reward circuitry. Developmental Science, 14(2), F1-F10. https://onlinelibrary.wiley.com/doi/full/10.1111/j.1467-7687.2010.01035.x?casa_token=p-yGKbDac1QAAAAA%3A4Izut7nFS3tC7gjkeQWO7r5wIM4UMzqUHMFVzgH5GpR1pZbJwlh9EMYo_IjpLtdAyocfoXVtHn5TaAQ
Steinberg, L., & Monahan, K. C. (2007). Age differences in resistance to peer influence. Developmental psychology, 43(6), 1531. https://psycnet.apa.org/record/2007-16709-020
Additional Reading
Blakemore, S. J. (2018). Inventing ourselves: The secret life of the teenage brain. London, England: Doubleday.
Jensen, F. E. (2016). The Teenage Brain: A Neuroscientist's Survival Guide to Raising Adolescents and Young Adults. New York, USA: Harper Collins.
Lebel, C., & Beaulieu, C. (2011). Longitudinal development of human brain wiring continues from childhood into adulthood. Journal of Neuroscience, 31(30), 10937-10947.
