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Risk rush
2011-05-19 11:45:11
19 May 2011 Last updated at 08:24 Share this page Delicious Digg Facebook reddit StumbleUpon Twitter Email Print Teenagers' brains 'linked to recklessness' By Michael Mosley 'Inside the Human Body' presenter
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//Video: National Institutes of Health
Each of the hundred billion brain cells you were born with makes, on average, 10,000 different connections. It happens so fast that the basics of the brain's architecture are laid down by the time you are six.
From birth until you hit puberty, your brain goes on growing.
And then something truly astonishing happens. Instead of making new connections, from about 12 onwards you start to lose them.
'Ruthlessly pruned'In the video you can see what looks like a wave of blue travelling from the back of the brain (on the left) towards the front (on the right), as brain connections start to die off.
During the teenage years you lose about one per cent of your brain's grey matter every year.
This might appear to be bad news, a sign your brain is already going downhill. It is anything but.
During the teenage years, your brain is being reshaped. It is a bit like a sculptor who starts off with a great big block of marble. To create a stunning statue, the sculptor has to chip away, slowly turning the uniform block into a thing of beauty.
What is happening in the teenage years is that your brain is being de-cluttered. Unnecessary or unused connections are ruthlessly pruned.
Continue reading the main story “Start QuoteWhenever a teenager takes a risk, like driving a car too fast, the brain is rewarded with a hormonal rush”
End QuoteThat is why the teenage years are so critical to your future development. Skills and habits laid down then are likely to persist.
This pruning process will, in time, make the teenager's brain faster and more powerful. But, significantly, the scans show the last bit of the brain to reach full maturity is the bit at the front, the prefrontal cortex.
The prefrontal cortex is the part of the brain which is responsible for things like planning, anticipating, controlling your own emotions and understanding them in others - in short, being grown up.
If you don't have a fully functioning prefrontal cortex you tend to be impulsive, insensitive to other people's feelings and take unnecessary risks.
As well as lacking some of the essential braking mechanisms on impulsive behaviour that the prefrontal cortex provides, teenage brains also seem to have the brain accelerator firmly pressed down.
Whenever a teenager takes a risk, like driving a car too fast, the brain is rewarded with a hormonal rush, a much stronger natural high than an adult would feel.
One explanation why teenagers might be wired to be reckless is that being a risk-taker also encourages us to explore the world, to try out a range of new things.
Modern brain imaging, by enabling us to see inside a teenager's brain, may make parents more sympathetic.
Once we realise that a lot of bad behaviour may be partly a product of the unfinished wiring inside teenagers' heads, perhaps we will be a little bit more forgiving.
Michael Mosley presents Inside the Human Body - Building Your Brain on BBC One at 9pm on Thursday 19 May 2011 or catch up on all 4 episodes on BBC iPlayer