The Washington University School of Medicine researchers in St. Louis said their study of one of the human brain's most fundamental "foundations" is an important step forward in outlining what neuroscientists call the functional architecture of the brain. Better understanding of that architecture, they said, will aid efforts to treat brain injuries and mental disorders.

"A different, more labile and higher-frequency signal known as the gamma frequency activity has been the focus of much brain research in recent years," said graduate student Biyu He, the study's first author. "But we found that signal loses its large-scale structure in deep sleep, while the low-frequency signal does not, suggesting that the low-frequency signal may be more fundamental."

"What we've been finding is reorienting the way we think about how the brain works," said Dr. Marcus Raichle, a professor of radiology, neurology and neurobiology.

The complex research and its findings were reported in the online early edition of the Proceedings of the National Academy of Science.