Today, we had a genuinely great talk by Professor Bob Knight.
TITLE: Neural Oscillations Track Behavior in the Human Cortex
ABSTRACT: Since the discovery of the EEG in 1920’s, neurophysiological dogma for the ensuing 80 years stated that the human cortex did not generate reliable rhythms above 50-60 Hz. However, findings over the last decade reliably report neural activity up to 250 Hz in the human cortex. This high frequency activity is the key neural response measuring cortical activation in humans. We record the human electrocorticogram (ECoG) from subdural electrodes implanted directly on the cortex of neurosurgical patients. We have observed that every cognitive process examined including language, attention, memory and motor control generates high frequency oscillatory activity in the range of 70-250 Hz (high gamma, HG). Importantly, the HG band of the human ECoG has the most precise spatial localization and task specificity of any frequency observed. For instance, during linguistic processing, HG precisely tracks the spatio-temporal evolution from comprehension in posterior temporal areas to production structures in the left frontal region. HG a precisely tracks the time course of the behavior needed to comprehend the word, select a noun and articulate a response all occurring within a second. Similar findings of HG activity are observed for working memory, contextual processing and a host of other human behaviors. Importantly the HG response can be reliably extracted at the single trial level providing a powerful tool for studying the physiology of human behavior. HG is also phase locked to the trough of theta rhythms in the human neocortex parallel to findings of HG-theta coupling observed in animal hippocampus and cortex. HG-theta coupling occurs in a task specific manner with different cognitive tasks eliciting unique distributed spatial patterns of HG-theta coupling. These results indicate that transient coupling between low- and high-frequency brain rhythms provide a mechanism for effective communication in distributed neural networks engaged during cognitive processing in humans. Taken together the results indicate that HG activity provides a powerful new tool for understanding the real-time cortical dynamics subserving cognition in humans.
BIO: Dr. Knight received his BS in Physics from the Illinois Institute of Technology in 1970 and his MD from Northwestern University Medical School in 1974. He did Neurology residency at the University of California at San Diego followed by post-doctoral work at the Salk Institute for Biological Studies in the area of human neurophysiology. He was a faculty member in the Department of Neurology at the University of California at Davis School of Medicine from 1980-1998. In 1998 Dr. Knight moved to UC Berkeley to lead a program in human neuroscience. He is currently the Evan Rauch Professor of Neuroscience and Director of the Helen Wills Neuroscience Institute at UC Berkeley. His laboratory utilizes electrophysiological and MRI techniques in neurological and neurosurgical patients to delineate the role of prefrontal cortex in human cognitive and social behavior. His laboratory also records electrocorticographic activity directly from the human cortex from neurosurgical patients in an effort to delineate the cortical mechanisms supporting behavior. His laboratory is also involved in developing neural prosthesis devices for motor and language restoration in patients with stroke or spinal cord injury using electrocorticographic recordings. Dr. Knight received the Jacob Javits Award from the National Institute of Neurological Disorders and Stroke for distinguished contributions to understanding neurological disorders, the IBM Cognitive Computing Award and the 2008 German Humboldt Prize in Neurobiology.
