14 DAY TRIAL // Sleep researchers at the University of California in Berkeley (UCB) say they may have found an explanation for why people's brains tend to remain in a light, restless type of activity during a large portion of the time they are asleep, rather than going into REM.
The rapid-eye-movements (REM) stage is considered to be that dreamy, deep sleep, which is the most comforting. Yet the brain spends only a small part of the time it's asleep in this state.
For the rest of the time, brain activity persists at low, but detectable levels. During this phase, sleep can be characterized as restless, the UCB team says. Sleep experts have been wondering as to the reasons why sleeping patterns are divided in this way for many years.
Scientists now believe that light sleep may be responsible for recharging our batteries in a way, allowing our brains to replenish their capacity to sustain the learning process, PsychCentral reports.
As evidence, the team points to sleep spindles, which are bursts of brain waves that they say play an important role in clearing the path for the formation of new memories, and for enabling further learning. The spindles are also involved in networking key regions of the brain together.
The way this is done is by clearing the hippocampus, an area of the brain with limited memory storage space, and which mostly contains fact-based memories. By transferring the data to the prefrontal cortex, a genuine human hard drive, sleep effectively reboots the hippocampus.
This allows the structure to be able to process, learn and store new data when a person awakes. Spindles are not generated during REM sleep, and they play an important role in the brain, considering that they can take place up to 1,000 times per night.
“All these pieces of the puzzle tell a consistent and compelling story – that sleep spindles predict learning refreshment,” explains UCB associate professor of psychology and neuroscience Dr. Matthew Walker, the senior author of the new study.
A paper describing the findings is scheduled to be published in an upcoming issue of the esteemed scientific journal Current Biology. The findings also have implications for the way people set up their sleeping hours.
“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,” adds expert Dr. Bryce Mander.
“You will have fewer spindles, and you might not be able to learn as much,” says the scientist, who is a postdoctoral fellow in psychology at UCB. He is also the lead author of the upcoming study.