Some people wake up at the drop of a pin; others snooze through their alarms every morning. Whether you can sleep through noise has a lot to do with the brain waves you produce while you sleep, according to a new study published in Current Biology. And good news for insomniacs: it might one day be possible to manipulate these waves to ensure a good night’s rest.

Previous research has shown that when people sleep, the thalamus—a brain structure that connects the high-level thought areas with the sights and sounds of the outside world—produces brief, high-frequency brain waves called spindles. Scientists speculated that these spindles shut out environmental sounds during sleep. To find out, Jeffrey Ellenbogen, chief of the division of sleep medicine at Harvard University’s Massachusetts General Hospital, and his colleagues asked 12 healthy people to spend three nights in his sleep lab. The first night the researchers measured spindle activity while the subjects slept individually in quiet rooms. The second and third nights the researchers relentlessly bombarded each snoozing participant with recordings of common noises such as toilets flushing, phones ringing and people talking, starting each noise at a low volume and repeating it more and more loudly until the subject was aroused from sleep. Then they repeated the process as soon as the person fell asleep again.

The researchers discovered that “the more spindles one has, the more likely they are able to stay asleep when they are confronted with sounds,” Ellenbogen explains. Compared with subjects who produced few spindles on the first night, those who produced many had to be bombarded with louder sounds to wake up. Because spindle production dwindles with age, the findings could explain why older people frequently complain of poor sleep.

In future research, Ellenbogen plans to explore why some people produce more spindles than others. Eventually he hopes to find drugs or devices that will boost natural spindle production and induce better sleep. “The capacity of our brain to block out at least some sound is truly amazing, given that our ears are wide open all night long,” he says.

This article was originally published with the title Things That Go Bump in the Night.

4 Comments

1. 1. Nathaniel 12:45 PM 10/31/10

   I had to learn how to be a light sleeper. I used to live close to train tracks and could sleep through the train and the horn blowing. I eventually moved away from there and got a girlfriend who was prone to dangerous sleepwalking. There were times when I had to physically restrain her to keep her from hurting herself in her sleep. As such, I learned to gently lift out of sleep, evaluate the situation based completely on sound, and then either fall back asleep or get up and handle the situation. I've also become good enough at lucid dreaming that I can realize when my hands have fallen asleep (like when you're laying on them), wake up just enough to become aware of my real body, change position, and then go back to being completely sleep. It's taken years and years to perfect these techniques to this point, but it is probably the most useful thing about my sleep habits that I've developed thus far.

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2. 2. JamesDavis 02:19 PM 10/31/10

   That would be great if they can bring the spindles up to normal levels for each person's normal level of hearing. Bringing the spindles higher may be dangerous since they respond chemically to sounds that make us uncomfortable. I find the sound of heavy thunder storms comforting when I sleep, so I can sleep better during a thunder storm and the sound of my dog walking around in the room. An uncomfortable sound like a spoon falling off the counter in the kitchen will wake me up.
   
   Before you make a chemical that increases spindles, you should know what sounds are comfortable and uncomfortable for the person. I reckon a good audiologist could determine the proper milligram.

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3. 3. Cosmic 02:21 PM 10/31/10

   As the previous commenter, I learned to be a light sleeper (or to turn off my spindles) when I had young children. I always slept with one ear open or perhaps it would be more accurate to say, with all my spindles on. Now that I no longer have children at home, I sleep more deeply.

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4. 4. Luminous 03:54 PM 11/2/10

   When I was 15 I spent three weeks gaining sea experience on a Hull fishing trawler in the Arctic Circle north of Iceland. As a guest I had to sleep on a setee (couch) next to a bulkhead, on the other side of which was a steam winch used for hauling and shooting the net. On the fishing grounds when fishing was good, the net would be hauled in every 2 hour, making a very loud racket as a ratchet mechanism clattered away. At first I thought it impossible to sleep through this noise, and my strategy was to turn in immediately the gear had been shot, in the hope of getting a couple of hours sleep. But soon I was sleeping through multiple net cycles.
   
   Later I had a sea career on large ocean going freighters and slept through many a storm where my fellow officers complained they had been unable to sleep either for the noise or because of the violent motion.
   
   Now I am in my 60's and still enjoy a good sleep, 8 hours when I can get it. I am thankful my spindles still seem to be ok.
   
   

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