Tune-up During Sleep Boosts Memory
Electric Current Improves Memory When Applied During Early Sleep Period
Nov. 6, 2006 -- Sleep boosts memory. An electric current that tunes the
brain during early sleep can improve memory even more, German scientists
During sleep, your brain consolidates the things you learned during the day.
When you wake, you can remember these things better than you could the night
before. How does this happen?
Memory boosting happens early in sleep, during the period of slow-wave sleep
that comes before dreaming and rapid-eye-movement (REM) sleep. During this
time, the electric currents in the brain slowly oscillate up and down.
Some scientists say these oscillations are good vibrations that bring brain
networks carrying new information into harmony with the rest of the brain.
Other scientists say these vibrations are just a side effect of the brain
trying to synchronize itself.
Lisa Marshall, PhD, Jan Born, PhD, and colleagues at the University of
Lubeck thought of a way to test these ideas. They got 13 brave volunteers --
mostly medical students -- to let them place electrodes on their heads. While
the students slept, the researchers turned on a mild electric current. The
pulsing current tuned the student's brains to a slow frequency.
For an hour and a half before going to sleep, the students studied a list of
paired words. They were tested just before sleeping and just after waking up
the next morning. As expected, the students did better the next morning. But
they did even better when their brains were electronically tuned.
"This improvement in retention following stimulation is striking
considering that most subjects were medical students, who were highly trained
in memorizing facts and already performed well in the sham condition,"
Marshall and colleagues note.
The brain tuning improved memory only when given during early, slow-wave
sleep and not during other phases of the sleep cycle.
The researchers conclude that the slow vibrations of early sleep are not the
mere humming of the brain while it works on more important things. Instead,
they may be the music of which memories are made.
Marshall and colleagues report the findings in the early online edition of
the journal Nature.