Electrocorticographic Mapping of Expressive Language Function without Requiring the Patient to Speak: A Report of Three Cases
National Center for Adaptive Neurotechnologies,Wadsworth Center, New York State Department of Health Albany United States
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Objective Patients requiring resective brain surgery often undergo functional brain mapping during perioperative planning to localize expressive language areas. Currently, all established protocols to perform such mapping require substantial time and patient participation during verb generation or similar tasks. These issues can make language mapping impractical in certain clinical circumstances e.g., during awake craniotomies or with certain populations e.g., pediatric patients. Thus, it is important to develop new techniques that reduce mapping time and the requirement for active patient participation. Several neuroscientific studies reported that the mere auditory presentation of speech stimuli can engage not only receptive but also expressive language areas. Here, we tested the hypothesis that submission of electrocorticographic ECoG recordings during a short speech listening task to an appropriate analysis procedure can identify eloquent expressive language cortex without requiring the patient to speak. Methods Three patients undergoing temporary placement of subdural electrode grids passively listened to stories while we recorded their ECoG activity. We identified those sites whose activity in the broadband gamma range 70170 Hz changed immediately after presentation of the speech stimuli with respect to a prestimulus baseline. Results Our analyses revealed increased broadband gamma activity at distinct locations in the inferior frontal cortex, superior temporal gyrus, andor perisylvian areas in all three patients and premotor andor supplementary motor areas in two patients. The sites in the inferior frontal cortex that we identified with our procedure were either on or immediately adjacent to locations identified using electrical cortical stimulation ECS mapping...