Heavy sleepers' brains don't 'hear' noise

CAMBRIDGE, Mass., Aug. 10 (UPI) -- Heavy sleepers sleep through almost anything because their brains are better at fending off noises, U.S. researchers say.

Scientists as Harvard University say such sleepers are able to block outside noise from getting to their brains and are more like to manage a night of undisturbed sleep, a university release said Monday.

Researchers at the school studying brainwaves found that the mind produces pulses called "spindles" during sleep that stop noises from getting to the part of the brain that would make the sleeper aware of them, the release said.

Electroencephalography patterns in the brain, used to distinguish stages of sleep, show slow brain waves were interspersed with brief rapid pulses, or spindles.

The brain activity producing spindles, which only occurs during sleep, kept sensory information from passing through an area of the brain known as the thalamus.

Electrical signals pass through the thalamus on the way to the cortex, where sounds are perceived by the mind. So if the signals stop in the thalamus, the person does not become aware of the noise.

The research showed most people keep a consistent spindle rate and that those with higher rates were less likely to be disturbed on noisy nights.