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“During slow-wave sleep, there is this release,
What happens to your a kind of beautiful set of interactions between
different brain areas, that is specialised, and it
looks different than what we see during awake
memories when you sleep? periods,” says Anna Schapiro, also at Harvard
Medical School. There is conversation between
regions key to memory, including the
hippocampus, where recent memories are
stored, and the cortex, where long-term
memories end up. This chatter might be
allowing the cortex to pull out and save
important information from new memories.
We don’t need to recall everything that
happened in a day, and sleep favours certain
types of memory. It homes in on information
that might be useful at a later date, and puts it
into longer-term storage. Schapiro has found,
for example, that merely telling people they
will be tested on certain material helps them
remember more of it after sleep.
Memories with an emotional component
also get preferential treatment – especially
“ Sleep will help to preserve
a really intense memory,
but decrease the emotionality”
negative emotions. That makes sense from
an evolutionary perspective if we are to
remember our mistakes and so increase our
chances of survival.
However, there are also hints that sleep
might help to modulate emotional memories.
“If you have a memory that was really intense,
sleep will help to preserve the memory, but
THIERRY ARDOUIN/TENDANCE FLOUE “Post traumatic stress disorder might actually
decrease the emotionality,” says Schapiro.
This could be crucial for our mental health.
be a direct consequence of failures of those
sleep-dependent processes that weaken the
intensity of emotional responses to
memories,” says Stickgold.
It could also help explain why getting too
little sleep is so bad for you. Negative
HERE is an old wives’ tale that putting your parts of a memory to retain. And it links memories become dominant over neutral and
revision notes under your pillow the night new memories with established networks positive ones, for a start. We end up less wise
T before an exam will make you remember of remembrances. It discovers patterns and too, says Stickgold. “We remember facts and
more. That might be stretching the truth, rules, says Stickgold, “and it’s doing this events, but don’t manage to figure out what
but there could be something in it – you really every night, all night long.” they really mean for us and our future.”
do learn in your sleep. One of the biggest unanswered questions And what about advice for anyone with
You don’t need sleep to create a memory. is how the sleeping brain knows which exams on the horizon? “It’s much better to go
“But sleep plays a critical role in determining memories to strengthen, and which to ignore. to sleep between studying and taking a test
what happens to these newly formed “We don’t know either the algorithms the than to stay awake all night studying,” says
memories,” says Bob Stickgold at Harvard brain uses to make these decisions, or how Schapiro. So put those notes under your pillow
Medical School. Sleep determines what goes they are implemented,” says Stickgold. and get some shut-eye. Your brain should do
into long-term storage. It can also select which What we do know is that sleep is special. the rest. Catherine de Lange
34 | NewScientist | 27 October 2018
