March 11, 2011

Sleep And Learning

(Ivanhoe Newswire) -- Why do we sleep?  I mean, we spend so much of our time sleeping that it must be doing something important.  It seems pretty simple right?  Not exactly.  There are myriad theories about rapid eye movement (REM) sleep, however, scientists have spent many sleepless nights determining why we spend so many hours in light, dreamless slumber.  Well, according to a new-fangled study, it is suggested that we are busy recharging our brain's learning capacity during this traditionally undervalued phase of sleep, which can take up half the night.

Researchers at UC Berkeley have discovered convincing evidence that bursts of brain waves commonly referred to as "sleep spindles" may be networking between key regions of the brain in order to clear a path to learning.  These electrical impulses assist in shifting fact-based memories from the brain's hippocampus "“ which has limited storage space "“ to the prefrontal cortex's "hard drive," thus freeing up the hippocampus to take in new data.  Spindles are fast pulses of electricity generated throughout non-REM sleep, and moreover can occur up to 1,000 times a night.

"All these pieces of the puzzle tell a consistent and compelling story "“ that sleep spindles predict learning refreshment," which Matthew Walker, associate professor of psychology and neuroscience at UC Berkeley and senior author of the study, was quoted as saying.
It was also reported that this spindle-driven networking was most likely to occur during Stage 2 of non-Rapid Eye Movement (NREM) sleep, which occurs before we reach the deepest NREM sleep and the dream state known as Rapid Eye Movement (REM) sleep.  This shallow stage of dreamless slumber can account for half our sleeping hours, and happens most commonly throughout the second half of the night, or in the latter part of a period in which we sleep.

"A lot of that spindle-rich sleep is occurring the second half of the night, so if you sleep six hours or less, you are shortchanging yourself.  You will have fewer spindles, and you might not be able to learn as much," which Bryce Mander, a post-doctoral fellow in psychology at UC Berkeley and lead author of the study, was quoted as saying.

As for broader societal ramifications, researchers reported evidence that brain waves during the latter part of the sleep period promote our ability to store fact-based memories raises the question of whether the early school day is most advantageous for learning.

"These findings further highlight the importance of sleep in our educational populations, where the need for learning is great, yet late bedtimes and early school start times prevent adequate sleep amounts," Mander added.

Walker and his team of sleepless scientists took 44 hale and hearty young adults and subjected them to meticulous memorization tasks intended to tax the hippocampus.  All of the participants performed at comparable levels.  The group was then divided, with one half taking a 90-minute nap while the other half stayed wide awake.

That evening, the whole group was subjected to another round of intensive learning.  The capability to memorize novel information deteriorated for those who had remained awake throughout the day. In contrast, those who had napped not only performed better than the waking group, but also improved their capability for learning, as if sleep had refreshed their memory capacity.

"Our findings demonstrate that sleep may selectively seek out and operate on our memory systems to restore their critical functions," Walker concluded.  "This discovery indicates that we not only need sleep after learning to consolidate what we've memorized, but that we also need it before learning, so that we can recharge and soak up new information the next day."

SOURCE: Current Biology, 8 March 2011