Sleep 'boosts brain cell numbers'

Scientists believe they have discovered a new reason why we need to sleep - it
replenishes a type of brain cell.
Sleep ramps up the production of cells that go
on to make an insulating material known as
myelin which protects our brain's circuitry.
The findings, so far in mice, could lead to
insights about sleep's role in brain repair and
growth as well as the disease MS, says the
Wisconsin team.
The work is in the Journal of Neuroscience.
Dr Chiara Cirelli and colleagues from the
University of Wisconsin found that the
production rate of the myelin making cells,
immature oligodendrocytes, doubled as mice
slept.
The increase was most marked during the type
of sleep that is associated with dreaming -
REM or rapid eye movement sleep - and was
driven by genes.
In contrast, the genes involved in cell death
and stress responses were turned on when the
mice were forced to stay awake.
Precisely why we need to sleep has baffled
scientists for centuries. It's obvious that we
need to sleep to feel rested and for our mind
to function well - but the biological processes
that go on as we slumber have only started to
be uncovered relatively recent

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