02945nas a2200289 4500008004100000022001400041245010600055210006900161260001200230300000700242490000600249520210500255653001102360653002502371653001802396653001002414653001102424100001902435700001802454700002402472700002202496700001802518700002902536700002302565700001902588856004802607 2012 eng d a1662-516100aTemporal evolution of gamma activity in human cortex during an overt and covert word repetition task.0 aTemporal evolution of gamma activity in human cortex during an o c05/2012 a990 v63 a

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.

10acortex10aElectrocorticography10agamma rhythms10ahuman10aSpeech1 aLeuthardt, E C1 aPei, Xiao-Mei1 aBreshears, Jonathan1 aGaona, Charles, M1 aSharma, Mohit1 aFreudenberg, Zachary, V.1 aBarbour, Dennis, L1 aSchalk, Gerwin uhttp://www.ncbi.nlm.nih.gov/pubmed/22563311