Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Brain Signal Persists Even in Dreamless Sleep

02.10.2008
Neuroscientists at Washington University School of Medicine in St. Louis have taken one of the first direct looks at one of the human brain's most fundamental "foundations": a brain signal that never switches off and may support many cognitive functions.

The results, appearing online this week in The Proceedings of the National Academy of Sciences, are an important step forward for efforts to outline what neuroscientists call the functional architecture of the brain. Better understanding of this architecture will aid efforts to treat brain injury and mental disorders.

Although the brain's different specialized regions can be considered as a collection of physical structures, functional architecture instead focuses on metaphorical structures formed by brain processes and interactions among different brain regions. The "foundation" highlighted in the new study is a low-frequency signal created by neuronal activity throughout the brain. This signal doesn't switch off even in dreamless sleep, possibly to help maintain basic structure and facilitate offline housekeeping activities.

"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," says first author Biyu He, a graduate student. "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," says senior author Marcus Raichle, M.D., professor of radiology, of neurology and of neurobiology. "We're starting to see the brain as being in the prediction business, with ongoing, organized carrier frequencies within the systems of the brain that keep them prepared for the work they need to do to perform mental tasks."

Neurologists have already spent many years exploring the upper levels of the brain's functional architecture. In these studies, researchers typically ask volunteers to perform specific mental tasks as their brains are scanned using functional magnetic resonance imaging (fMRI). Such "goal-oriented" tasks might include looking for or studying a visual stimulus, moving an arm or leg, reading a word or listening for a sound. As the subjects perform these tasks, the scans reveal increases in blood flow to different parts of the brain, which researchers take as indications that the brain areas are contributing to the mental task.

In the past decade, though, scientists have realized that deeper structures underlie goal-oriented mental processes. These underlying brain processes continue to occur even when subjects aren't consciously using their brain to do anything, and the energies that the brain puts into them seem to be much greater than those used for goal-oriented tasks.

"The brain consumes a tremendous amount of the body's energy resources—it's only 2 percent of body weight, but it uses about 20 percent of the energy we take in," says Raichle. "When we started to ask where all those resources were being spent, we found that the goal-oriented tasks we had studied previously only accounted for a tiny portion of that energy budget. The rest appears to go into activities and processes that maintain a state of readiness in the brain."

To explore this deeper level of the brain's functional architecture, Raichle and others have been using fMRI to conduct detailed analyses of brain activity in subjects asked to do nothing. However, a nagging question has dogged those and other fMRI studies: Scientists assumed that increased blood flow to a part of the brain indicates that part has contributed to a mental task, but they wanted more direct evidence linking increased blood flow to stepped-up activity in brain cells.

In the new study, He and her colleagues took fMRI scans of five patients with intractable epilepsy at St. Louis Children's Hospital. The scans, during which the subjects did nothing, were taken prior to the temporary installation of grids of electrodes on the surfaces of the patients' brains. The level of detail provided by the grids is essential clinically for pinpointing the source of the seizures for possible surgical removal, a last resort employed only when other treatments failed.

Patients and their guardians gave permission to use the clinical data gathered from these electrodes for scientific research purposes. He's results confirmed that the fMRI data she had gathered earlier reflected changes in brain cell activity exhibited in the gamma frequency signal. But she also noticed the persistent low-frequency signal, which also corresponded to the fMRI data.

"When we looked back in the literature, we found that a similar signal had been the subject of a great deal of animal research using implanted electrodes in the 1960s through the 1980s," she says. "There were suggestions, for example, that when this low-frequency signal, which fluctuates persistently, is in a low trough, the brain may handle mental tasks more effectively."

"What we've shown provides a bridge between the fMRI work many scientists are doing now and the earlier work involving electrical recordings from the brain that emphasized slow activity," says He. "Bringing those two fields together may give us some very interesting insights into the brain’s organization and function."

He BJ, Snyder AZ, Zempel JM, Smyth MD, Raichle ME. Electrophysiological correlates of the brain's intrinsic large-scale functional architecture. Proceedings of the National Academy of the Sciences, online edition.

Funding from the National Institutes of Health supported this research.

Washington University School of Medicine's 2,100 employed and volunteer faculty physicians also are the medical staff of Barnes-Jewish and St. Louis Children's hospitals. The School of Medicine is one of the leading medical research, teaching and patient care institutions in the nation, currently ranked third in the nation by U.S. News & World Report. Through its affiliations with Barnes-Jewish and St. Louis Children's hospitals, the School of Medicine is linked to BJC HealthCare.

Michael C. Purdy | Newswise Science News
Further information:
http://www.wustl.edu

More articles from Health and Medicine:

nachricht An ounce of prevention: Research advances on 'scourge' of transplant wards
28.08.2015 | University of Wisconsin-Madison

nachricht Hypoallergenic parks: Coming soon?
27.08.2015 | American Society of Agronomy

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: OU astrophysicist and collaborators find supermassive black holes in quasar nearest Earth

A University of Oklahoma astrophysicist and his Chinese collaborator have found two supermassive black holes in Markarian 231, the nearest quasar to Earth, using observations from NASA's Hubble Space Telescope.

The discovery of two supermassive black holes--one larger one and a second, smaller one--are evidence of a binary black hole and suggests that supermassive...

Im Focus: What would a tsunami in the Mediterranean look like?

A team of European researchers have developed a model to simulate the impact of tsunamis generated by earthquakes and applied it to the Eastern Mediterranean. The results show how tsunami waves could hit and inundate coastal areas in southern Italy and Greece. The study is published today (27 August) in Ocean Science, an open access journal of the European Geosciences Union (EGU).

Though not as frequent as in the Pacific and Indian oceans, tsunamis also occur in the Mediterranean, mainly due to earthquakes generated when the African...

Im Focus: Self-healing landscape: landslides after earthquake

In mountainous regions earthquakes often cause strong landslides, which can be exacerbated by heavy rain. However, after an initial increase, the frequency of these mass wasting events, often enormous and dangerous, declines, in fact independently of meteorological events and aftershocks.

These new findings are presented by a German-Franco-Japanese team of geoscientists in the current issue of the journal Geology, under the lead of the GFZ...

Im Focus: FIC Proteins Send Bacteria Into Hibernation

Bacteria do not cease to amaze us with their survival strategies. A research team from the University of Basel's Biozentrum has now discovered how bacteria enter a sleep mode using a so-called FIC toxin. In the current issue of “Cell Reports”, the scientists describe the mechanism of action and also explain why their discovery provides new insights into the evolution of pathogens.

For many poisons there are antidotes which neutralize their toxic effect. Toxin-antitoxin systems in bacteria work in a similar manner: As long as a cell...

Im Focus: Fraunhofer IPA develops prototype of intelligent care cart

It comes when called, bringing care utensils with it and recording how they are used: Fraunhofer IPA is developing an intelligent care cart that provides care staff with physical and informational support in their day-to-day work. The scientists at Fraunhofer IPA have now completed a first prototype. In doing so, they are continuing in their efforts to improve working conditions in the care sector and are developing solutions designed to address the challenges of demographic change.

Technical assistance systems can improve the difficult working conditions in residential nursing homes and hospitals by helping the staff in their work and...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Networking conference in Heidelberg for outstanding mathematicians and computer scientists

20.08.2015 | Event News

Scientists meet in Münster for the world’s largest Chitin und Chitosan Conference

20.08.2015 | Event News

Large agribusiness management strategies

19.08.2015 | Event News

 
Latest News

Interstellar seeds could create oases of life

28.08.2015 | Physics and Astronomy

An ounce of prevention: Research advances on 'scourge' of transplant wards

28.08.2015 | Health and Medicine

Fish Oil-Diet Benefits May be Mediated by Gut Microbes

28.08.2015 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>