[Paleopsych] Newswise: Study Shows How Sleep Improves Memory

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Study Shows How Sleep Improves Memory
http://www.newswise.com/p/articles/view/512800/
     Source: [1]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
     injuries.

     "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
     preserving memory.

     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
     brain.

     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
     the clock.

     "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 [2]http://www.bidmc.harvard.edu.