Nimg-63. gamma-band modulations of electrocorticogram (ecog) induced by cognitive-linguistic tasks during awake craniotomy for feasible functional language mapping

Abstract INTRODUCTION Intraoperative functional language mapping has uncertainty in predicting language function and post-surgical outcomes. We study the feasibility of functional mapping using electrocorticogram (ECoG) gamma-band modulations induced by linguistic tasks having different complexity levels. METHODS Five subjects with left temporal lobe glioma underwent resection involving awake language mapping using a 4x8 ECoG electrode grid. A MATLAB/Simulink based real-time software system was used to map task-induced gamma-band modulations as 2D heat maps. Tasks included verbally responding to single word/tone categorization; object, action, written descriptive and auditory naming respectively. Auditory stimuli were provided during word/tone categorization (duration 300~500ms) and auditory naming tasks ( > 1s). Other tasks provided visual stimuli (line drawings or written phrases). Bipolar DCS (2~6 mA, 60Hz, 2s) was applied at different electrode pairs while repeating the naming tasks. RESULTS Cortical regions activated by word stimuli and the auditory naming task were similar; superior, middle temporal gyri (STG, MTG). Visual naming tasks modulated posterior MTG (pMTG) and STG (written naming). Reproducible speech arrests occurred during different naming tasks while stimulating specific electrode pairs, even though not all electrodes had strong task-specific activations. Considerable inter-personal variability of language areas identified with DCS was observed, despite the similarity of task-specific gamma-band modulated regions across subjects. Post-operative decline in language score was observed in one subject, with resection boundary covering gamma modulated regions during auditory processing tasks but no DCS identified region. CONCLUSION Intraoperative language mapping guided by gamma-band ECoG modulations induced by simple word/tone categorization task exhibited similar patterns to more complex naming tasks, suggesting this task may be a viable approach to localize functional cortex, especially in patients unable to reliably perform more difficult paradigms. Utilizing this method in conjunction with DCS mapping guided by visual naming tasks, eloquent cortical language areas may be better preserved reducing post-operative language deficits.