By Calvin Palmer
If you are one of those people who can sleep through violent thunderstorms or other loud noises during the night, it is because your brain produces more sleep spindles, say scientists.
Researchers at the Harvard Medical School in Boston have found that the brain produces brief bursts of electrical activity – sleep spindles – to block out sound during sleep.
“The more sleep spindles your brain produces, the more likely you’ll stay asleep, even when confronted by noise,” said researcher Dr Jeffrey Ellenbogen.
Brain activity producing spindles, which only occur during sleep, keeps 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 are stopped in the thalamus, the person does not become aware of the noise.
In short, light sleepers do not produce as many sleep spindles as heavy sleepers.
“Given that the brain already has a mechanism in place to reduce the impact of noises on the sleeping brain, my laboratory is seeking to understand how the brain achieves that block and what we can do to enhance this naturally occurring protection of sleep from noises,” said Ellenbogen.
As part of the study, 12 adults spent three nights under observation, with EEG readings being taken constantly. The first night was spent in quiet conditions, with the subsequent two involving increasing levels of sound.
The results revealed that each person kept a consistent spindle rate – the same on each night, regardless of decibel levels – and that those with higher rates were less likely to be disturbed on the noisy nights.
Participants often were not aware that their sleep had been interrupted – indicating that environmental noise can have a greater impact on sleep quality than an individual may realize, the researchers said.
“Our goal is to find brain-based solutions that integrate a sleeping person into their modern environment, such that sleep is maintained even in the face of noises,” Ellenbogen said. “This finding gets us one important step closer to realising that goal.”
A report of the study appears in the journal Current Biology.