Turn me on, turn me off: Sleep soon a switch away

Last Updated: Monday, April 30, 2007 | 7:53 PM ET

CBC News

Getting a good night's sleep could soon be as easy as flipping a switch — literally, according to U.S. researchers.

Magnetic waves can be used to stimulate the brain in a way that generates the brainwaves characteristic of the deepest phase of sleep, according new research by Giulio Tononi, a University of Wisconsin-Madison psychiatry professor.

The discovery, whose details are to be published in PNAS, a journal of the Proceedings of the National Academy of Sciences of the United States, could theoretically be used to stimulate a nap that has the restorative properties of eight hours of sleep, according to the scientist.

In the so-called slow-wave activity, electrical activity flows across the brain about once a second, or 1,000 times per night. The slow-wave activity occurs for about 80 per cent of the time that a person is asleep. The more sleep a person has, the more the activity weakens.

Tononi and his team, including colleague Marcello Massimini at the school in Madison, Wis., used a technique called transcranial magnetic stimulation (TMS) to create the slow waves in sleeping volunteer test subjects.

"With a single pulse, we were able to induce a wave that looks identical to the waves the brain makes normally during sleep," Tononi said in a written statement.

The research was prompted by a growing belief in the scientific community that slow waves perform a critical role in sleep and its restorative effects.

"We have reasons to think the slow waves are not just something that happens, but that they may be important," Tononi said, adding that he believes they "clear out the noise to make sure your brain does not become too much of an energy hog, a space hog. By morning, you have a brain that is energy efficient, space efficient and ready to learn again."

Tononi theorizes that sleep weakens "bonds,"  synapses formed and strengthened in the brain during waking hours — including inadvertent bonds formed by unconsciously absorbing information and experiences around us. This weakening in turn reduces the organ's physical demands on a person.

"It is wonderful that you can have all these synaptic traces in the brain, but they come at a price. Synapses require proteins, fats, space and energy. At the end of a waking day, you have all these traces of memories left behind."

He said without the weakening effect that he believes occurs during sleep, people would be incapable of learning new things because the brain would lack enough energy, space and nutrients.