Berkeley - It is well known that the output of nerve cells is the messenger of information between regions of the brain, yet it is still unclear about how widely separated regions of the cortex involving billions of cells come together to assist a complex activity. A new study by neuroscientists at the University of California, Berkeley, and neurosurgeons and neurologists at UC San Francisco (UCSF) is getting to resolve this mystery.
UCSF neurosurgeons place 64-electrode grids on the surface of the brain's temporal and frontal lobes to locate regions where epileptic seizures originate. These grids allowed UC Berkeley neuroscientists to study the interaction of brain waves during simple tasks, such as word recognition or hand movements. (Images courtesy the Knight Lab)
"One of the most important questions in neuroscience is: How do areas of the brain communicate?" said Dr. Robert Knight, professor of psychology, Evan Rauch Professor of Neuroscience and director of the Helen Wills Neuroscience Institute at UC Berkeley. "A simple activity like responding to a question involves areas all over the brain that hear the sound, analyze it, extract the relevant information, formulate a response, and then coordinate your lips and mouth to speak. We have no idea how information moves between these areas."
By measuring electrical activity in the brains of pre-surgical epilepsy patients, the researchers have found the first evidence that slow brain oscillations, or theta waves, "tune in" the fast brain oscillations called high-gamma waves that signal the transmission of information between different areas of the brain. In this way, the researchers argue, areas like the auditory cortex and frontal cortex, separated by several inches in the cerebral cortex, can coordinate activity.
"If you are reading something, language areas oscillate in theta frequency allowing high-gamma-related neural activity in individual neurons to transmit information," said Knight. "When you stop reading and begin to type, theta rhythms oscillate in motor structures, allowing you to plan and execute your motor response by way of high gamma. Simple, but effective."
The findings are reported in the Sept. 15 issue of Science.