[Paleopsych] Newswise: Study Shows How Sleep Improves Memory
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Fri Jul 1 17:37:25 UTC 2005
Study Shows How Sleep Improves Memory
Source: Beth Israel Deaconess Medical Center
Released: Tue 28-Jun-2005, 11:05 ET
Newswise -- A good night's sleep triggers changes in the brain that
help to improve memory, according to a new study led by researchers at
Beth Israel Deaconess Medical Center (BIDMC).
These findings, reported in the June 30, 2005, issue of the journal
Neuroscience and currently published on-linee, might help to explain
why children - infants, in particular - require much more sleep than
adults, and also suggest a role for sleep in the rehabilitation of
stroke patients and other individuals who have suffered brain
"Our previous studies demonstrated that a period of sleep could help
people improve their performance of `memory tasks,' such as playing
piano scales," explains the study's lead author Matthew Walker, PhD,
director of BIDMC's Sleep and Neuroimaging Laboratory. "But we didn't
know exactly how or why this was happening.
"In this new research, by using functional magnetic resonance imaging
(fMRI), we can actually see which parts of the brain are active and
which are inactive while subjects are being tested, enabling us to
better understand the role of sleep to memory and learning."
New memories are formed within the brain when a person engages with
information to be learned (for example, memorizing a list of words or
mastering a piano concerto). However, these memories are initially
quite vulnerable; in order to "stick" they must be solidified and
improved. This process of "memory consolidation" occurs when
connections between brain cells as well as between different brain
regions are strengthened, and for many years was believed to develop
merely as a passage of time. More recently, however, it has been
demonstrated that time spent asleep also plays a key role in
In this new study, twelve healthy, college-aged individuals were
taught a sequence of skilled finger movements, similar to playing a
piano scale. After a 12- hour period of either wake or sleep,
respectively, the subjects were tested on their ability to recall
these finger movements while an MRI measured the activity of their
According to Walker, who is also an Assistant Professor of Psychiatry
at Harvard Medical School, the MRI results showed that while some
areas of the brain were distinctly more active after a period of
sleep, other areas were noticeably less active. But together, the
changes brought about by sleep resulted in improvements in the
subjects' motor skill performance.
"The cerebellum, which functions as one of the brain's motor centers
controlling speed and accuracy, was clearly more active when the
subjects had had a night of sleep," he explains. At the same time, the
MRIs showed reduced activity in the brain's limbic system, the region
that controls for emotions, such as stress and anxiety.
"The MRI scans are showing us that brain regions shift dramatically
during sleep," says Walker. "When you're asleep, it seems as though
you are shifting memory to more efficient storage regions within the
brain. Consequently, when you awaken, memory tasks can be performed
both more quickly and accurately and with less stress and anxiety."
The end result is that procedural skills - for example, learning to
talk, to coordinate limbs, musicianship, sports, even using and
interpreting sensory and perceptual information from the surrounding
world -- become more automatic and require the use of fewer conscious
brain regions to be accomplished.
This new research may explain why children and teenagers need more
sleep than adults and, in particular, why infants sleep almost round
"Sleep appears to play a key role in human development," says Walker.
"At 12 months of age, infants are in an almost constant state of motor
skill learning, coordinating their limbs and digits in a variety of
routines. They have an immense amount of new material to consolidate
and, consequently, this intensive period of learning may demand a
great deal of sleep."
The new findings may also prove to be important to patients who have
suffered brain injuries, for example, stroke patients, who have to
re-learn language, limb control, etc.
"Perhaps sleep will prove to be another critical factor in a stroke
patient's rehabilitation," he notes, adding that in the future he and
his colleagues plan to examine sleep disorders and memory disorders to
determine if there is a reciprocal relationship between the two.
"If you look at modern society, there has in recent years been a
considerable erosion of sleep time," says Walker. Describing this
trend as "sleep bulimia" he explains that busy individuals often
shortchange their sleep during the week - purging, if you will - only
to try to catch up by "binging" on sleep on the weekends.
"This is especially troubling considering it is happening not just
among adults, but also among teenagers and children," he adds. "Our
research is demonstrating that sleep is critical for improving and
consolidating procedural skills and that you can't short-change your
brain of sleep and still learn effectively."
Study co-authors include BIDMC researchers Gottfried Schlaug, MD, PhD,
Robert Stickgold, PhD, David Alsop, PhD and Nadine Gaab, PhD.
This study was supported by grants from the National Institutes of
Health and the Dana Foundation.
Beth Israel Deaconess Medical Center is a patient care, teaching and
research affiliate of Harvard Medical School, and ranks third in
National Institutes of Health funding among independent hospitals
nationwide. BIDMC is clinically affiliated with the Joslin Diabetes
Center and is a research partner of Dana-Farber/Harvard Cancer Center.
BIDMC is the official hospital of the Boston Red Sox. For more
information, visit http://www.bidmc.harvard.edu.
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