04 March 2011

“Honey? Are you awake?” and alpha waves

Pity poor Hans Berger.

The man changed our understanding of human experience and human consciousness, but didn’t know how he did it, was largely ignored in his life, and committed suicide.

In the mid 1920s, Berger invented the electroencephalagraph (EEG), a technique for measuring the electrical activity of brains. Unfortunately, Berger didn’t understand electricity very well, so didn’t have a clear understanding of what his recordings might mean. But he revolutionized the study of human brains.

Perhaps nowhere was Berger’s invention put to greater use than in the study of sleep. Before that, what did we know of brains while we slept? For all we knew, the brain activity dialed down to almost nothing each night. With the use of EEGs, we discovered the very distinct stages of sleep.

ResearchBlogging.orgBerger’s invention continues to deepen our understanding of sleep, nearly a century after its invention, as shown by a new paper by KcKinney and colleagues.

McKinney and colleagues claim to have an indicator of how deep asleep you are on a much finer time scale than previously possible.

An EEG signal is a complicated, wavy line. But because it is a wave, you can describe it as a combination of other, simpler waves through a mathematical technique called Fourier analysis or power analysis. McKinney and colleagues say that the waves of one particular frequency, about 8-13 times a second, correlates very closely with how loud a sound has to be for someone to be roused from sleep.

Now, if you could make one of those devices portable so that one person could wear it and broadcast it locally, their partners staying up late would be able to pick the time they were least likely to wake up their snoozing partners.


McKinney S, Dang-Vu T, Buxton O, Solet J, & Ellenbogen J. 2011. Covert waking brain activity reveals instantaneous sleep depth. PLoS ONE 6(3): e17351. 10.1371/journal.pone.0017351

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