Why sleep is shrinking your brain

Scientists say parts of our brain shrink when we sleep – and that's a good thing!

And no, it doesn't mean we are losing thought capacity or intelligence, instead it means our brains are taking advantage of the decreased brain traffic and getting the rest it needs to "renormalise".

Sleep is believed to be the best time for this process because we are free from the external world and the “here and now".

Scientists say parts of our brain shrink when we sleep - and we are becoming smarter for it. Source: Getty

Dr Chiara Cirelli and Giulio Tononi, researchers at the University of Wisconsin-Madison Centre for Sleep and Consciousness, found evidence that our brain synapses - the connections between nerve cells - shrink by 20 per cent while sleeping.

They made the discovery by looking at the brains of a group of mice over four years and found that their neuron connections decreased in size at night to reset.

This process is known as "synaptic homeostasis" and is believed to be a chance for neurons to create room for more growth and learning for the next day.

Scientists suggested this process could be a reason why sleep exists among animals universally. Source: Getty

In fact, scientists suggested it could be a reason why sleep exists among animals universally – to recharge our brains for further learning.

"Sleep is the perfect time to allow the synaptic renormalisation to occur... because when we are awake, we are 'slaves' of the here and now, always attending some stimuli and learning something," Dr Cirelli told Live Science.

"During sleep, we are much less preoccupied by the external world and the brain can sample (or assess) all our synapses, and renormalise them in a smart way."

Microscope pictures from inside the brains of mice suggest what happens in our own brain every day. Source:University of Wisconsin–Madison

Chief researcher at the centre, Luisa de Vivo, found that the contact area where the two neurons meet, somehow manages to shrink evenly yet maintain stable memory traces, Live Science reported.

De Vivo also says the strongest synapses – memories you are unlikely to forget – were unaffected by the nighttime downscaling.

“They may be the repositories of very strong memories – like the name of your mum – which you’re very unlikely to forget, even if you’re sleep-deprived,” Dr Cirelli added.

"The majority of synapses, which are scaled down, may be the ones more engaged in what happened recently. If they’re not linked to anything relevant over a few days, they disappear. That’d be my guess.”

It takes a lot of energy to maintain brain connections and researchers say that without sleep we may suffer an "information overload". Source: Getty

It takes a lot of energy to maintain brain connections and researchers say that without sleep our neurons may become twitchy and hyperactive – think a case of "information overload."

Richard Huganir from Johns Hopkins University and his group separately researched the theory and in particular the receptor proteins – tiny docking stations allowing the transfer of brain connections, which are found at synapses.

They isolated large numbers of the synapses from the brains of mice, both asleep and awake, and found that the receptors moved away from the synapses while the animals slept.

The contact area where the two neurons meet, somehow manages to shrink evenly yet maintain stable memory traces. Source: Getty

“In theory, the system could get to total saturation – all synapses would be strong and couldn’t get any stronger, and you wouldn’t be able to encode any more information” Huganir said.

Researchers say the next step is to follow the very same synapses over time to see how animals change physically, learn new tasks, fall asleep, and wake up.

So all in all, sleep is the price we pay for an ever-evolving brain that are able to keep us learning new things.

Information on this report came from the University of Wisconsin-Madison's science journal and Live Science.

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