Why do we sleep? To forget irrelevant memories, study says

About 33 per cent of our lifetimes are either spent sleeping or trying to sleep. And although many of us know that getting adequate rest is beneficial to our overall health, we’ve struggled to really know the reason why we sleep in the first place.

Now, new research shows that sleep may help the brain forget irrelevant memories in order to make room for new information.

Two new papers published in the journal Science suggest that sleep is vital toward restoring the correct balance of synapses — the connecting points between neurons in the brain.

During sleep, the synapses undergo some major alterations in signalling; they rest and get ready for the following day when you’re awake — where they’ll grow and allow for more information that’s gathered to travel throughout the brain. Study findings revealed that the synapses in mice that slept for a few hours decreased by about 18 per cent compared to mice that stayed awake.

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Since memories are stored as molecular changes at these connection points, sleep can help us forget irrelevant information of the day to effectively make room for learning new things the next day, according to researchers.

“Sleep is the perfect time to allow the synaptic renormalization to occur … because when we are awake, we are ‘slaves’ of the here and now, always attending some stimuli and learning something,” study co-author Dr. Chiara Cirelli told Live Science.

According to researchers, the synapses shrinking or “pruning” during sleep is simply the body taking advantage of the decreased brain traffic that occurs during that period. They also noticed that the largest synapses were spared, speculating that they may be linked to important memories that the brain doesn’t want to lose.

If we don’t sleep, the studies suggest that the brain could get hit with a ton of irrelevant memories and information, which would inhibit our brains to function properly.

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“During sleep, we are much less preoccupied by the external world … and the brain can sample [or assess] all our synapses, and renormalize them in a smart way,” Cirelli noted.

Studies also show that sleep deprivation can negatively affect your physical and mental health, lead to weight gain, a decreased libido, fatigue, depression, and emotional stability issues.

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