Everything you need to know about the

Teen Brainto know about the

Teen Brain

Significant brain growth and development occurs during adolescence and continues into the twentiesduring adolescence, and continues into the twenties.

Some studies show that this growth and development extends to the age of 30!

(Sowell et al., 1999; Sowell et al., 2001)

development extends to the age of 30!

Adolescent brain development can be dividedAdolescent 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 volumeProliferation: Total brain volume

By age 6, the brain is about 95% of its maximum size.

It reaches its maximum* It reaches its maximum size at 11.5 years in girls*, and at 14.5 years g , yin boys*. (Giedd et al., 1999)*Boys brains are larger (on average) than girlsb i

Lenroot & Giedd (2006)

brains.

Remember…

Maximum brain size does not mean

maximum brain maturity!

The brain continues to mature for at least another 10 years.

Remember…

And although boysAnd although boysbrains are anatomically bigger than girls brains,bigger than girls brains,

size is not directly related to intelligence.

The tissue of the brain can be divided into twoThe tissue of the brain can be divided into two types of matter, grey and white. These

ti d t t diff t ttissues grow and mature at different rates.

White matter looks whiteto the naked eye and is

Grey matter looks grey to the naked eye. It is

f to the naked eye, and is made up of axons.

composed of neuron cell bodies, dendrites, and glial cellscells.

Grey matter is where all the thinking happens This is yourthinking happens. This is your

brain’s processing centre.

White matter, containing those long axons, are like a super highway. They transport information to different parts of your brainof your brain.

Photo credit (CC 2.0): facemepls, MSVG

Proliferation: Grey MatterProliferation: Grey Matter

G tt d lGrey matter develops quickly during childhood, but slows during adolescence.

Grey matter volume peaks at age 11 in girls and at g gage 13 in boys.

Then, the volume of grey

Lenroot & Giedd (2006)

matter begins to decline.

Pruning: Grey Matter MaturationPruning: Grey Matter Maturation

The maturation of grey matter is best described as a constant “push and pull” Newas 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”!it really is a case of use it or lose it !

This makes the adolescent brain extremely This makes the adolescent brain extremely versatile, and able to make changes depending on the demands of the environmentdepending on the demands of the environment.

Pruning: Grey Matter MaturationPruning: Grey Matter MaturationThe brain matures in a back-to-front pattern The frontalThe brain matures in a back-to-front pattern. The frontal & temporal lobes are the last to mature.

Remember: the frontal lobe is the home of planningRemember: the frontal lobe is the home of planning, organization, judgment, impulse control and reasoning!

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Lenroot & Giedd (2006)

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Proliferation and Myelination: White matterProliferation 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

*increase during puberty.

The increase occurs just after the peak in grey matter volume (around

*peak in grey matter volume (around age 11 in girls* and around age 13 in boys*).

Lenroot & Giedd (2006)

Say that again?!Say that again?!Teens show a consistent pattern

fof brain development.

White matter increases in a roughly linear pattern. The

pattern is similar in different

Grey matter follows an upside-down U shape. The pattern differs

according to brain regionpattern is similar in different brain regions.

according to brain region.

White Grey

The Teen Brain is in a Constant State of Development

And some areas of the brain t f t th th Thmature faster than others. The

areas of your brain associated with reward motivation andwith reward, motivation, and impulsivity matures early.

Photo credit (CC 2.0): Daniel Flower

The Teen Brain is in a Constant State of Development

Your prefrontal cortexYour prefrontal cortex, which thinks about things logically weighs the proslogically, weighs the pros and cons, and restrains you matures later. This ymeans teens can be more prone to riskier and impulsive behaviors, and less likely to consider consequences than anconsequences than an adult would be.

Photo credit (CC 2.0): Alaskan Dude

Risk and RewardRisk 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 anythose behaviors outweigh any potential harm.

Reyna & Farley (2007) Photo credit (CC 2.0): winnifredxoxo

Risk and RewardRisk and Reward

It’s important to take a step back and realize that though notback 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 the rest of your life in a really

Playing Russian Roulette with one bullet is certainly much safer than playing it

negative way.much safer than playing it

with five. But should we really be playing it at all?

Photo credit (CC 2.0): Andres BastidasReyna & Farley (2007)

So how does the brain So how does the brain mature after adolescence?

There is evidence that these changes continue WELL

fafter the teenage years.

In a study of young adults, the frontal lobes showed large changes up to the age of 30!showed large changes up to the age of 30!

This suggests that frontal lobe maturation is

(Sowell et al., 1999; Sowell et al., 2001)

important for adult cognition.

What does all this mean?

It means huge advances have been made in studies

of brain development.p

BUTit is difficult to figure out

BUT…it is difficult to figure out

exactly how these structural brain changes

relate to functional changes in cognition and behavior.

Hopefully, the answers to these questions will come these questions will come within the next few years.

ReferencesReferencesGiedd J N Blumenthal J Jeffries N O Castellanos F X Liu H Zijdenbos AGiedd, J.N., Blumenthal, J., Jeffries, N.O., Castellanos, F.X., Liu, H., Zijdenbos, A., Paus, T., Evans, A.C., Rapoport, J.L. 1999. Brain development during childhood and adolescence: 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 Biobehavioral Reviews. 30: 718-729.

Sowell, E.R., Thompson, P.M., Holmes, C.J., Jernigan, T.L., Toga, A.W. 1999. In vivo evidence for post-adolescent brain maturation in frontal and striatal regions. Nature Neuroscience 2: 859-861Neuroscience. 2: 859-861.

Sowell, E.R., Thompson, P.M., Toga, A.W. 2001. Mapping continued brain growth and gray matter density reduction in dorsal frontal cortex: Inverse relationships during postadolescent brain maturation. The Journal of Neuroscience. 21: 8819-8829.

Reyna V F and Farley F 2007 Is the teen brain too rational? Scientific AmericanReyna, V. F. and Farley, F. 2007. Is the teen brain too rational? Scientific American Mind. 17: 58-65

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