Washington State University sleep scientist Jonathan Wisor has received a $1.3 million grant from the National Institutes of Health to delve deeper into the links between sleep and brain metabolism.

The four-year project will examine why the brain's use of glucose drops sharply during sleep. Glucose is used as an energy source by the body. The brain uses it to fuel its electrical activity, a metabolically demanding process that accounts for as much as 25 percent of the body's glucose use, even though the brain only represents about 5 percent of body mass.

Preliminary data collected by Wisor show that it's the slow-wave phase of sleep—also known as deep sleep—that is responsible for the brain's decrease in glucose metabolism.

"During slow-wave sleep, all of the neurons go through transient periods where they are completely inactive; they're not discharging electrical activity," says Wisor, an assistant professor with the WWAMI medical education program in Spokane who also has research ties with the WSU Sleep and Performance Research Center and the Department of Veterinary and Comparative Anatomy, Pharmacology, and Physiology (VCAPP) in the College of Veterinary Medicine. "We're trying to determine what it is about sleep that reduces the demand for glucose relative to the waking brain."

Using an animal model, WSU claims Wisor's study will be the first to apply what's called high-temporal resolution technique to measure changes in glucose metabolism over a short time span—as brief as seconds—while simultaneously measuring the brain's electrical activity through electroencephalography (EEG). The two variables will be measured continuously during normal waking and sleeping activity, as well as during sleep deprivation.

The hypothesis for the study is that glucose utilization and slow-wave sleep are in a mutual regulatory relationship. Wisor describes it as a "clean-up" process through which the brain uses slow-wave sleep to reduce glucose use to reset its metabolic balance. He uses as a metaphor the operation of a coal-fired electricity plant, which requires regular shutdowns of the furnace to clear out soot and ash to return it to optimal working condition.

If his hypothesis holds true, it might offer a functional explanation for why we sleep, Wisor asserts.

"We know that sleep is a restorative process," he says. "This set of biochemical changes may be the restorative basis for sleep in its simplest, most fundamental form."

The study also could lead to insights into medical conditions in which brain metabolism is compromised, he says.

"If we can understand the brain's use of glucose in the context of the normal, healthy sleeping brain, there are potential applications for situations in which the brain becomes extremely metabolically vulnerable, such as during stroke, diabetes, and complications of childbirth," Wisor says.

WSU Spokane is an urban campus of Washington State University, a land-grant research university founded in 1890. The campus is home to advanced studies and research in health sciences and health professions, the design disciplines, education, social and policy sciences, and science and technology.

Washington State University is one of 95 public and private research universities with "very high" research activity, according to the Carnegie Foundation for the Advancement of Teaching classifications.