How sleep improves memory
Almost a century after the discovery
that sleep helps us remember things, scientists are now beginning
to understand why. The Society for Neuroscience has discovered that
it comes down to the active chemicals in your brain, while you are
During sleep, the brain produces
chemicals which relive events that we want to remember; making the
memories important and therefore more permanent. "One of the most
profound effects of a night of sleep is the improvement in our
ability to remember things," says Ravi Allada, a sleep researcher
at Northwestern University.
"Sleep is also a time when old
memories can be modified and new memories can be formed." says
Karim Benchenane from the National Center for Scientific Research
in Paris. Benchenane was part of a team that studied the brains of
rats while they were both awake and asleep.
When the animals were awake and
moving around their cages, the scientists identified brain cells
that only became active when the rats were in a specific location.
During sleep, these same cells became active in the same order,
showing that the rats were reliving their travels and presumably
strengthening their memories of places they'd been.
Then Benchenane's team set out to
change each rat's memory during sleep. They did this by stimulating
the pleasure centre in the animal's brain each time the brain cell
associated with a specific location became active. The idea was to
form a positive association with one place in the cage. Sure
enough, when the animals woke up, they went straight to that
location, looking for a positive reward.
"The finding not only shows that new
memories can be formed during sleep, but it also suggests a new way
to treat people who have post-traumatic stress disorder and often
have a negative association with a particular experience." says
One surprising bit of research in
the same study found that having a midnight snack can undo the
memory benefits of getting enough sleep. The researchers found that
people who wake up in the night and want to snack should try and
resist if they want their memory to work normally the next