People who were able to sleep despite a noisy environment showed different brain-wave rhythms in recent research. (J. Pat Carter/Associated Press)

A rhythm in our sleeping brains may help explain why some people can doze through nearly any noise while others awaken at the slightest peep.

A sensory gateway in the brain's thalamus seems to play an important role in blocking out noise during sleep, scientists say in Tuesday's online issue of the journal Current Biology.

In the study, researchers observed recordings of brain-wave patterns in 12 volunteers with an average age of 26 who agreed to sleep in a noisy sleep laboratory.

The first night, the subjects enjoyed quiet surroundings. But over the next two nights, they were subjected to sounds, including a telephone ringing, people talking, traffic and mechanical sounds such as the type often heard in hospitals.

Brain waves become slow and organized during sleep. Brief bursts of faster-frequency waves, known as sleep spindles, are also produced and stood out on EEGs in the study, said study author Dr. Jeffrey Ellenbogen of Harvard Medical School in Boston.

"The more sleep spindles your brain produces, the more likely you'll stay asleep, even when confronted by noise," Ellenbogen, chief of the division of sleep medicine at Massachusetts General Hospital, said in a release.

The spindle rhythms are generated by the thalamus, which helps relay most sensory information to the brain.

Spindles put spin on sleep

In the experiment, volunteers with higher rates of spindle rhythms tended to sleep through the noisy nights compared to those with lower rates.

Spindle rates were consistent from night to night, the team found.

"Our data raise important questions about whether augmenting spindle rate through behaviour, drug or device might protect sleep by harnessing the spindle’s ability to deflect incoming stimuli," the study's authors concluded.

It's not yet clear how to do so. But such an advance would be welcome in a modern world full of electronic beeps, particularly such hospital sounds as the alarms on monitors, Ellenbogen said.

In the meantime, he suggests putting up a sign that says "Shhh!"

Another tip for those who must fall asleep to radio or TV is to use a timer, since research suggests such noises disrupt sleep even if the person doesn't realize it.

This study was funded by the Academy of Architecture for Health, the Facilities Guidelines Institute, the Centre for Health Design and Massachusetts General Hospital.