UC Berkeley researchers have found compelling evidence that bursts of brain waves known as “sleep spindles” may be networking between key regions of the brain to clear a path to learning.

These electrical impulses help to shift 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 fresh data. Spindles are fast pulses of electricity generated during non-REM sleep, and they can occur up to 1,000 times a night.

“Sleep spindles predict learning refreshment,” said Matthew Walker, associate professor of psychology and neuroscience at UC Berkeley. “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,” said Bryce Mander, a post-doctoral fellow in psychology at UC Berkeley and lead author of the study.

Their work appears March 8 in the journal Current Biology

The study found that spindle-driven networking was most likely to happen 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 frequently during the second half of the night, or in the latter part of a period in which we sleep.

Electroencephalogram tests measured electrical activity in the brains of the nappers and showed that the more sleep spindles the nappers produced, the more refreshed they were for learning. Researchers were able to link sleep spindles to brain activity looping between the lobes of the brain that house the hippocampus and prefrontal cortex — two critical areas for memory.

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

Adapted from materials provided by University of California – Berkeley