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Tianyi Qian, Wenjing Zhou, Zhipei Ling, Shangkai Gao, Hesheng Liu, and Bo Hong

provide a direct measure of the neural activity on the brain surface. Various brain functions can modulate the ECoG signal, especially in the high-frequency band. During certain body movement tasks, significant power increase in high gamma oscillations (> 60 Hz) 9 , 11 , 30 has been observed. Task-induced or evoked high gamma activity was also reported in the sensory motor cortex, 22 , 24 , 28 , 48 visual cortex, 27 , 53 , 57 frontal eye field, 32 and olfactory 42 and speech-related areas. 5 , 7 , 10 , 13 , 33 , 38 , 54 , 58 The spatial distribution of high gamma

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Yukie Tamura, Hiroshi Ogawa, Christoph Kapeller, Robert Prueckl, Fumiya Takeuchi, Ryogo Anei, Anthony Ritaccio, Christoph Guger, and Kyousuke Kamada

electrocorticography (ECoG) have been proposed as potential neurophysiological indicators. Among these oscillatory changes, augmentation of high gamma activity (HGA) from approximately 60 to 140 Hz was assumed to reflect localized cortical processing. Crone et al. constructed HGA maps of language-related functions in patients performing word-reading tasks, which were confirmed by ECS. 6 Therefore, HGA sheds light on the optimal signal for accurate functional mapping. We have reported a clinical user interface for real-time HGA mapping in awake craniotomy, with combinations of

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Kyousuke Kamada, Hiroshi Ogawa, Christoph Kapeller, Robert Prueckl, Satoru Hiroshima, Yukie Tamura, Fumiya Takeuchi, and Christoph Guger

for treatment. In addition to fMRI, functional networks can be mapped electrophysiologically using stimulus-response measures (electrocortical stimulation [ECS]) and by monitoring endogenous resting oscillatory activity. Among resting-state signals, high gamma activity (HGA) augmentation in the range of 60–170 Hz is assumed to reflect cortical center functioning. 4 , 19 , 20 Sinai et al. reported a detailed comparison of ECS and HGA mapping in patients with subdural grid implantation 23 and suggested their combined utility for preliminary network mapping. Several

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Carter D. Wray, Tim M. Blakely, Sandra L. Poliachik, Andrew Poliakov, Sharon S. McDaniel, Edward J. Novotny, Kai J. Miller, and Jeffrey G. Ojemann

-related desynchronization. 24 In hand motor tasks, these conjugate processes cause behavioral splits at 48 ± 9 Hz (± SD) to assess local cortical function. 17 , 18 Changes in power in high gamma activity during hand movement rapidly localize cortical hand area with only several seconds of data collection, giving a rapid, specific, and straightforward method for locating functional areas in the cortex with the hgECoG signal. Even imagining motor movement can activate these areas of cortex. 20 These 4 modalities of mapping sensorimotor function should produce concurrent results, but

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Emad Eskandar

significant improvement in clinical outcomes by minimizing the risk of neurological injury or enhancing the success of treating the underlying epilepsy. Disclosure The author reports no conflict of interest. Reference 1 Qian T , Zhou W , Ling Z , Gao S , Liu H , Hong B : Fast presurgical functional mapping using task-related intracranial high gamma activity. Laboratory investigation . J Neurosurg [epub ahead of print April 19, 2013. DOI: 10.3171/2013.2.JNS12843]

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David P. McMullen, Tessy M. Thomas, Matthew S. Fifer, Daniel N. Candrea, Francesco V. Tenore, Robert W. Nickl, Eric A. Pohlmeyer, Christopher Coogan, Luke E. Osborn, Adam Schiavi, Teresa Wojtasiewicz, Chad R. Gordon, Adam B. Cohen, Nick F. Ramsey, Wouter Schellekens, Sliman J. Bensmaia, Gabriela L. Cantarero, Pablo A. Celnik, Brock A. Wester, William S. Anderson, and Nathan E. Crone

candidate implant targets. The vibrotactile stimulation hardware is placed prior to incision ( D ). After the craniotomies ( E ), a 1 × 8 ECoG strip is placed for phase reversal mapping of the central sulcus ( F ). The novel intraoperative mapping, utilizing hd-ECoG arrays ( G ), is performed to refine finger-specific implant targeting. High gamma activity of vibrotactile stimulation of individual fingers is mapped onto ECoG figures ( H ). These results are combined and transferred manually to a diagram overlaid on intraoperative photographs ( I ) so that the team can

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David P. McMullen, Tessy M. Thomas, Matthew S. Fifer, Daniel N. Candrea, Francesco V. Tenore, Robert W. Nickl, Eric A. Pohlmeyer, Christopher Coogan, Luke E. Osborn, Adam Schiavi, Teresa Wojtasiewicz, Chad R. Gordon, Adam B. Cohen, Nick F. Ramsey, Wouter Schellekens, Sliman J. Bensmaia, Gabriela L. Cantarero, Pablo A. Celnik, Brock A. Wester, William S. Anderson, and Nathan E. Crone

candidate implant targets. The vibrotactile stimulation hardware is placed prior to incision ( D ). After the craniotomies ( E ), a 1 × 8 ECoG strip is placed for phase reversal mapping of the central sulcus ( F ). The novel intraoperative mapping, utilizing hd-ECoG arrays ( G ), is performed to refine finger-specific implant targeting. High gamma activity of vibrotactile stimulation of individual fingers is mapped onto ECoG figures ( H ). These results are combined and transferred manually to a diagram overlaid on intraoperative photographs ( I ) so that the team can

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Jeffrey G. Ojemann

. Neuroimage 43 : 245 – 249 , 2008 14 Sinai A , Bowers CW , Crainiceanu CM , Boatman D , Gordon B , Lesser RP , : Electrocorticographic high gamma activity versus electrical cortical stimulation mapping of naming . Brain 128 : 1556 – 1570 , 2005 15 Tamura Y , Ogawa H , Kapeller C , Prueckl R , Takeuchi F , Anei R , : Passive language mapping combining real-time oscillation analysis with cortico-cortical evoked potentials for awake craniotomy . J Neurosurgery [epub ahead of print March 18, 2016. DOI: 10.3171/20154.JNS15193

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Milena Korostenskaja, Po-Ching Chen, Christine M. Salinas, Michael Westerveld, Peter Brunner, Gerwin Schalk, Jane C. Cook, James Baumgartner, and Ki H. Lee

directly from the surface of the brain (electrocorticography [ECoG]) in patients with subdural grids implanted for clinical purposes readily detect and localize signal changes due to different auditory, motor, or language tasks. 10 , 24 Also, many studies have suggested that ECoG amplitudes in the high gamma band (> 70 Hz) may be most valuable for assessing the task-related activity of cortical neurons directly underneath the electrodes. 1 , 8 , 9 , 19 , 27 Therefore, task-related test batteries based on the analysis of ECoG high gamma activity can be successfully