Stimulating slow waves in brain may harbour insomnia cure

A scientist has increased hopes for insomnia treatment after having found how to artificially stimulate brain waves that characterize the deepest stage of sleep.

Washington, May 1 : A scientist has increased hopes for insomnia treatment after having found how to artificially stimulate brain waves that characterize the deepest stage of sleep.

The finding, by a professor of psychiatry at the University of Wisconsin-Madison School of Medicine and Public Health, reveals that creating slow waves on demand could someday lead to cure for insomnia.

Giulio Tononi, the professor, has discovered how to stimulate brain waves that characterize the deepest stage of sleep.

The brain function in question, called slow wave activity, is crucial to the refurbishment of mood and the ability to learn, think and remember, Tononi says.

During slow wave activity, which occupies about 80 percent of sleeping hours, waves of electrical activity wash across the brain, roughly once a second, 1,000 times a night.

In a paper being published this week in the Early Edition of the scientific journal PNAS, Tononi and colleagues, including Marcello Massimini, also of the UW-Madison School of Medicine and Public Health, described the use of transcranial magnetic stimulation (TMS) to set off slow waves in sleeping participants. The researchers recorded brain electrical activity with an electroencephalograph (EEG).

A TMS instrument sends a risk-free magnetic signal through the scalp and skull and into the brain, where it stimulates electrical impulses. In reaction to each burst of magnetism, the subjects' brains instantly produced slow waves distinctive of deep sleep.

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

The researchers have learned to trace the TMS device above a particular part of the brain, where it causes slow waves that travel all through the brain.

"We don't know why, but this is a very good place to evoke big waves that clearly travel through every part of the brain," Tononi says.

According to Tononi, scientists' interest in slow waves comes from a rising approval of their role in sleep.

"We have reasons to think the slow waves are not just something that happens, but that they may be important in sleep's restorative powers," Tononi says.

For example, a sleep-deprived person has larger and more numerous slow waves once asleep. And as sleep proceeds, Tononi adds, the slow waves weaken, which may signal that the need for sleep is partially satisfied.

Theoretically, slow waves could also lead to a magnetically enthused "power nap," which might bestow the benefit of eight hours sleep in just a few hours.

Based on the fact that sleep seems to "consolidate" memories, many neuroscientists believe that sleeping lets us run through the day's events.

Tononi agrees that sleep improves memory, but he thinks this happens through a different process, one that involves a drop in brain overwork. During sleep, he suggests, the synapses (connections between nerve cells) that were formed by the day's learning can relax a little.

While awake, we "observe and learn much more than you think," he observes. "Tons of things are leaving traces, changing the synapses, mainly by making them stronger. 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," Tononi adds.

"During the slow waves, all the connections, step by step, are becoming a little weaker," Tononi adds. "By morning, the total connection strength is back to the way it was the morning before. The trick is to downscale all the connections by the same percentage, so the ones that were stronger are still stronger. That way you don't lose the memory."

Without this type of weakening, he says, we "would not be able to learn new things" because our brains would be short of adequate available energy, space and nutrients.

Although the explanation is still a hypothesis, Tononi hopes that the ability to artificially stimulate slow waves will allow him and other researchers to test the notion that sleep restores the brain by damping connectivity between neurons.

Slow waves, he suspects, "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."

ANI