HOW SLEEP, MEMORY GO HAND IN HAND
Want to ace that test
tomorrow? Here's a tip: Put down the coffee and hit the sack.
Scientists have long
known that sleep, memory and learning are deeply connected. Most animals, from
flies to humans, have trouble remembering when sleep deprived, and studies have
shown that sleep is critical in converting short-term into long-term memory, a
process known as memory consolidation.
But just how that
process works has remained a mystery.
The question is, does
the mechanism that promotes sleep also consolidate memory, or do two distinct
processes work together? In other words, is memory consolidated during sleep
because the brain is quiet, allowing memory neurons to go to work, or are memory
neurons actually putting us to sleep?
In a recent paper in
the journal eLife, graduate students Paula Haynes and Bethany
Christmann in the Griffith Lab make a case for the latter.
Haynes and Christmann
focused their research on dorsal paired medial (DPM) neurons, well-known memory
consolidators in Drosophila. They observed, for the first time,
that when DPM neurons are activated, the flies slept more; when deactivated,
the flies kept buzzing.
These memory
consolidators inhibit wakefulness as they start converting short-term to
long-term memory. All this takes place in a section of the Drosophila brain
called the mushroom body, similar to the hippocampus, where our memories are
stored. As it turns out, the parts of the mushroom body responsible for memory
and learning also help keep the Drosophila awake.
"It's almost as
if that section of the mushroom body were saying 'hey, stay awake and learn
this,'" says Christmann. "Then, after a while, the DPM neurons start
signaling to suppress that section, as if to say 'you're going to need sleep if
you want to remember this later.'"
Understanding how
sleep and memory are connected in a simple system, likeDrosophila, can
help scientists unravel the secrets of the human brain.
"Knowing that
sleep and memory overlap in the fly brain can allow researchers to narrow their
search in humans," Christmann says. "Eventually, it could help us
figure out how sleep or memory is affected when things go wrong, as in the case
of insomnia or memory disorders."
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