Like listeners adjusting a high-tech radio, scientists at Washington University School of Medicine in St. Louis have tuned in to precise frequencies of brain activity to unleash new insights into how the brain works.
"Analysis of brain function normally focuses on where brain activity happens and when," says Eric C. Leuthardt, MD. "What we've found is that the wavelength of the activity provides a third major branch of understanding brain physiology."
Researchers used electrocorticography, a technique for monitoring the brain with a grid of electrodes temporarily implanted directly on the brain's surface. Clinically, Leuthardt and other neurosurgeons use this approach to identify the source of persistent, medication-resistant seizures in patients and to map those regions for surgical removal. With the patient's permission, scientists can also use the electrode grid to experimentally monitor a much larger spectrum of brain activity than they can via conventional brainwave monitoring.
Scientists normally measure brainwaves with a process called electroencephalography (EEG), which places electrodes on the scalp.
Brainwaves are produced by many neurons firing at the same time; how often that firing occurs determines the activity's frequency or wavelength, which is measured in hertz, or cycles per second. Neurologists have used EEG to monitor consciousness in patients with traumatic injuries, and in studies of epilepsy and sleep.
In contrast to EEG, electrocorticography records brainwave data directly from the brain's surface.
"We get better signals and can much more precisely determine where those signals come from, down to about one centimeter," Leuthardt, assistant professor of neurosurgery, of neurobiology and of biomedical engineering, says. "Also, EEG can only monitor frequencies up to 40 hertz, but with electrocorticography we can monitor activity up to 500 hertz. That really gives us a unique opportu
|Contact: Michael C. Purdy|
Washington University School of Medicine