The frequency of when and where does the brain becomes active for many years can be a source of important insights, suggests a new study.
Researchers at the Washington University School of Medicine in St. Louis made the discoveries possible by a grid of electrodes temporarily installed directly on the surface of a patient's brain to help pinpoint the source of medication-resistant seizures.
Like listeners adjusting a high-tech radio, scientists have tuned in to precise frequencies of brain activity to unleash new insights into how the brain works.
Researchers used electrocorticography, a technique for monitoring the brain with a grid of electrodes temporarily implanted directly on the brain's surface.
Clinically, Eric C. Leuthardt and other neurosurgeons used this approach to identify the source of persistent, medication-resistant seizures in patients and to map those regions for surgical removal.
Scientists normally measure brainwaves with a process called electroencephalography (EEG), which places electrodes on the scalp.
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. 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 opportunity to study the complete physiology of brain activity," said Leuthardt.
The team used the grids to watch consciousness fade under surgical anesthesia and return when the anesthesia wears off. They found each frequency gave different information on how different circuits changed with the loss of consciousness, according to Leuthardt.
Their results also showed a series of changes that occurred in a specific order during loss of consciousness and then repeated in reverse order as consciousness returned.
The results appeared in the Proceedings of the National Academy of Sciences.