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Humans (and other animals) need sleep as much as they need water and oxygen, and considering we spend about a third of our lives doing it, it clearly serves an important function. But, despite many theories, much of sleep's purpose remains elusive.
Leading theories - and debates - focus on its role in brain repair and reorganisation. Taking a unique, multi-disciplinary approach, a new study,
published in the journal
Science Advances,
suggests it does both - it just depends on age.
In children around two and a half years old, the study found, synaptic growth and reorganisation, which underpins learning and memory formation, seems to be sleep's main purpose.
After that age, sleep becomes dominated by repair and cleaning, or maintenance - and the transition is not a gradual process, according to senior author Van Savage from Santa Fe Institute, US.
"One most surprising part of this finding is that this switch is very sharp and abrupt," he says, likening it to the transition that happens when water freezes to ice.
Their analysis also reveals that deep rapid eye movement (
REM) sleep, associated with vivid dreams, could be the primary driver of brain reorganisation in those early years.
Comment: Seems like not a week goes by that we don't hear about another asteroid or near earth object that is discovered hurtling towards our end of the Milky Way system. It really just seems a matter of time before one or more of these finds its way to Terra.
And by now, its clear, many of the world's governments know it:
Asteroid threat: ESA's ambitious Hera Planetary Defense Mission awards $153 million contract