The secret to a sound sleep lies inside the brain, researchers find

I am frequently amazed by my husband’s ability to sleep through all kinds of noises that cause me to wake in a flash -- car alarms, smoke detectors that are running low on batteries, and especially kids who have lost track of their favorite blankie in the middle of the night. Thanks to a new study being published in Tuesday’s edition of the journal Current Biology, I now know that his brain probably produces more sleep spindles than mine.

You see, while we’re sleeping, the thalamus -- the part of the brain that receives sensory input like sounds -- tries to relay information to the cortex, where the sounds are actually perceived. Sleep experts can see these transmissions on an electroencephalography test, or EEG.

But, scientists believe, sometimes the brain throws up roadblocks to prevent the cortex from being disturbed during crucial periods of sleep when memories are consolidated. These roadblocks are sleep spindles, which also have a characteristic appearance on an EEG.

Researchers from Harvard Medical School’s Division of Sleep Medicine and colleagues theorized that people whose brains produced a higher rate of sleep spindles would be rewarded with a sounder sleep.

To test their hypothesis, they convinced 12 volunteers to spend three nights in a sleep lab at Boston’s Massachusetts General Hospital. The first night, the volunteers were hooked up to an EEG machine to record their rate of spindle production during a night of quiet sleep. For the next two nights, the researchers did their best to disrupt the volunteers’ sleep with increasingly noisy sounds like ringing telephones and airplanes flying overhead.

And indeed, “those with higher spindle rates on the quiet night exhibited greater sleep stability during the noisy nights,” the researchers found.

The discovery raises the possibility that poor sleepers could be helped by medications or devices that boost their production of sleep spindles, the authors wrote.

The report is online here.

-- Karen Kaplan

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