The adolescent brain is best described as a work in progress. Our brains are about 90-95% of their maximum size by the time we are 6 years old, but they are definitely not finished changing! Massive changes continue to occur over the next 15-20 years, as connections within the brain are strengthened and refined. Adolescent brain development can be divided into three processes: proliferation, pruning and myelination.
Significant brain growth and development occursduring adolescence and continues into the twenties adolescence, twenties. Some studies show that this growth and development extends to the age of 30! (Sowell et al., 1999; Sowell et al., 2001)
Adolescent brain development can be divided into three processes:• Proliferation (rapid growth of brain matter and the formation of new connections within the brain)• Pruning (cutting away of unused or unimportant ti ) connections)• Myelination (insulating of brain pathways to make them faster and more stable) ) (Sowell et al., 1999; Sowell et al., 2001)
Proliferation: Total brain volume By age 6, the brain is about 95% of its maximum size. * It reaches its maximum size at 11.5 years in g girls*, and at 14.5 years , y in boys*. (Giedd et al., 1999) * Boys brains are larger (on average) than girls brains. b iLenroot & Giedd (2006)
Remember… Maximum brain size does not mean maximum brain maturity! The brain continues to mature for at least another 10 years.
Remember… And although boys brains are anatomically bigger than girls brains, size is not directly related to intelligence.
The tissue of the brain can be divided into two types of matter, grey and white. These tissues grow and mature at diff ti d t t different rates. t tGrey matter looks greyto the naked eye. It is White matter looks whitecomposed of neuron cell f to the naked eye, and is eyebodies, dendrites, and glial made up of axons.cells.cells
Grey matter is where all the thinking happens This is your happens. brain’s processing centre.White matter, containing thoselong axons, are like a superhighway. They transportinformation to different partsof your brain brain. Photo credit (CC 2.0): facemepls, MSVG
Proliferation: Grey Matter Grey matter develops G tt d l quickly during childhood, but slows during adolescence. Grey matter volume peaks at age 11 in girls and at g g age 13 in boys. Then, the volume of grey matter begins to decline.Lenroot & Giedd (2006)
Pruning: Grey Matter Maturation The maturation of grey matter is best described as a constant “push and pull”. New pathways grow, while others are pruned back. Pruning is greatly influenced by experience, so it really is a case of “use it or lose it”! ! This makes the adolescent brain extremely versatile, and able to make changes depending on the demands of the environment environment.
Pruning: Grey Matter Maturation The brain matures in a back-to-front pattern. The frontal pattern & temporal lobes are the last to mature. Remember: the frontal lobe is the home of planning planning, organization, judgment, impulse control and reasoning! mporal ontal Parietal Fro TemLenroot & Giedd (2006)
Proliferation and Myelination: White matter White matter makes up myelin, which insulates axons and speeds up the communication between neurons. It develops continuously from * birth onwards, with a slight increase during puberty puberty. * The increase occurs just after the peak in grey matter volume (around age 11 in girls* and around age 13 in boys*).Lenroot & Giedd (2006)
Say that again?! Teens show a consistent pattern of brain development. fWhite matter increases in a Grey matter follows an upside- roughly linear pattern. The down U shape. The pattern differspattern is similar in different according to brain region region. brain regions. White Grey
The Teen Brain is in aConstant State of DevelopmentAnd some areas of the brainmature f t th others. The t faster than th Thareas of your brain associatedwith reward, motivation, and reward motivationimpulsivity matures early. Photo credit (CC 2.0): Daniel Flower
The Teen Brain is in aConstant State of DevelopmentYour prefrontal cortex, cortexwhich thinks about thingslogically,logically weighs the prosand cons, and restrainsyyou matures later. Thismeans teens can be moreprone to riskier andimpulsive behaviors, andless likely to considerconsequences than anadult would be. Photo credit (CC 2.0): Alaskan Dude
Risk and Reward It’s not that teens are stupid, or have no control over their own brain. Studies have shown that teens know when they are engaging in risky behavior (like unprotected sex, drinking, or drugs). However they are more likely to think that the benefits of those behaviors outweigh any potential harm.Reyna & Farley (2007) Photo credit (CC 2.0): winnifredxoxo
Risk and Reward It’s important to take a step back and realize that though not every risky choice will result in harm – some will. It’s not enough to know there’s risk, you need to also understand the consequences. It could impact Playing Russian Roulette the rest of your life in a really with one bullet is certainly much safer than playing it negative way. with five. But should we really be playing it at all?Reyna & Farley (2007) Photo credit (CC 2.0): Andres Bastidas
So how does the brainmature after adolescence? There is evidence that these changes continue WELL after the teenage years. fIn a study of young adults, the frontal lobesshowed large changes up to the age of 30!This suggests that frontal lobe maturation isimportant for adult cognition. (Sowell et al., 1999; Sowell et al., 2001)
What does all this mean? It means huge advances have been made in studies of brain development. p
BUT… BUT it is difficult to figure out exactly how these structural brain changesrelate to functional changes in cognition and behavior.
Hopefully, the answers tothese questions will comewithin the next few years.
ReferencesGiedd, J.N., Blumenthal, J Jeffries N O Castellanos F.X., Liu, H., Zijdenbos, A.,Giedd J N Blumenthal J., Jeffries, N.O., Castellanos, F X Liu H Zijdenbos APaus, T., Evans, A.C., Rapoport, J.L. 1999. Brain development during childhood andadolescence: A longitudinal MRI study. Nature Neuroscience. 2: 861-863.Lenroot, R.K., Giedd, J.N. 2006. Brain development in children and adolescents:Insights from anatomical magnetic resonance imaging. Neuroscience and BiobehavioralReviews. 30: 718-729.Sowell, E.R., Thompson, P.M., Holmes, C.J., Jernigan, T.L., Toga, A.W. 1999. In vivoevidence for post-adolescent brain maturation in frontal and striatal regions. NatureNeuroscience. 859-861.Neuroscience 2: 859-861Sowell, E.R., Thompson, P.M., Toga, A.W. 2001. Mapping continued brain growth andgray matter density reduction in dorsal frontal cortex: Inverse relationships duringpostadolescent brain maturation. The Journal of Neuroscience. 21: 8819-8829.Reyna, V. F.Reyna V F and Farley F 2007 Is the teen brain too rational? Scientific American Farley, F. 2007.Mind. 17: 58-65
Sun Life Financial ChairIn Adolescent Mental Health For more information visitWWW.TEENMENTALHEALTH.ORG