@article {4095, title = {Differential roles of high gamma and local motor potentials for movement preparation and execution}, journal = {Brain-Computer Interfaces}, volume = {3}, year = {2016}, month = {May}, pages = {88-102}, abstract = {Determining a person{\textquoteright}s intent, such as the planned direction of their movement, directly from their cortical activity could support important applications such as brain-computer interfaces (BCIs). Continuing development of improved BCI systems requires a better understanding of how the brain prepares for and executes movements. To contribute to this understanding, we recorded surface cortical potentials (electrocorticographic signals; ECoG) in 11 human subjects performing a delayed center-out task to establish the differential role of high gamma activity (HGA) and the local motor potential (LMP) as a function of time and anatomical area during movement preparation and execution. High gamma modulations mostly confirm previous findings of sensorimotor cortex involvement, whereas modulations in LMPs are observed in prefrontal cortices. These modulations include directional information during movement planning as well as execution. Our results suggest that sampling signals from these widely distributed cortical areas improves decoding accuracy.}, keywords = {BCI, brain-computer interfaces, ECoG, Electrocorticography, sensorimotor systems}, doi = {https://doi.org/10.1080/2326263X.2016.1179087}, author = {Gunduz, Aysegul and Peter Brunner and Sharma, Mohit and Leuthardt, Eric C. and Ritaccio, Anthony L. and Pesaran, Bijan and Schalk, Gerwin} } @article {2210, title = {Temporal evolution of gamma activity in human cortex during an overt and covert word repetition task.}, journal = {Front Hum Neurosci}, volume = {6}, year = {2012}, month = {05/2012}, pages = {99}, abstract = {

Several scientists have proposed different models for cortical processing of speech. Classically, the regions participating in language were thought to be modular with a linear sequence of activations. More recently, modern theoretical models have posited a more hierarchical and distributed interaction of anatomic areas for the various stages of speech processing. Traditional imaging techniques can only define the location or time of cortical activation, which impedes the further evaluation and refinement of these models. In this study, we take advantage of recordings from the surface of the brain [electrocorticography (ECoG)], which can accurately detect the location and timing of cortical activations, to study the time course of ECoG high gamma (HG) modulations during an overt and covert word repetition task for different cortical areas. For overt word production, our results show substantial perisylvian cortical activations early in the perceptual phase of the task that were maintained through word articulation. However, this broad activation is attenuated during the expressive phase of covert word repetition. Across the different repetition tasks, the utilization of the different cortical sites within the perisylvian region varied in the degree of activation dependent on which stimulus was provided (auditoryor visual cue) and whether the word was to be spoken or imagined. Taken together, the data support current models of speech that have been previously described with functional imaging. Moreover, this study demonstrates that the broad perisylvian speech network activates early and maintains suprathreshold activation throughout the word repetition task that appears to be modulated by the demands of different conditions.

}, keywords = {cortex, Electrocorticography, gamma rhythms, human, Speech}, issn = {1662-5161}, doi = {10.3389/fnhum.2012.00099}, url = {http://www.ncbi.nlm.nih.gov/pubmed/22563311}, author = {Leuthardt, E C and Pei, Xiao-Mei and Breshears, Jonathan and Charles M Gaona and Sharma, Mohit and Zachary V. Freudenberg and Barbour, Dennis L and Gerwin Schalk} }