#High-Gamma-Mapping "Background of High Gamma Mapping"

Background of High Gamma Mapping


Functional brain mapping of eloquentcortex is an essential step when planning resective brain surgeries. Mapping techniques like electrical cortical stimulation (ECS)123and functional magnetic resonance imaging (fMRI)1 are well-established in clinical practice. However, these procedures might be demanding for the patient or provide limited spatial and temporal resolution. ECS can also trigger accidental seizures. A passive mapping procedure based on task-related activation of the high-gamma frequency band (>60 Hz) in electrocorticographic (ECoG) signals promises fast and precise mapping without the risk of causing pain or seizures14. This mapping procedure has repeatedly demonstrated that it can accurately identify cortical regions related to receptive56 and expressive67 language function, motor function5689 and the somatosensory system5.


1. Tharin, S. & Golby, A. Functional brain mapping and its applications to neurosurgery. Oper. Neurosurg. 60, 185–202 (2007).

2. Ojemann, G. A. Cortical organization of language. J. Neurosci. 11, 2281–2287 (1991).

3. Crone, N. E. et al. Functional mapping of human sensorimotor cortex with electrocorticographic spectral analysis. Brain 121, 2271–2299 (1998).

4. Lachaux, J.-P., Axmacher, N., Mormann, F., Halgren, E. & Crone, N. E. High-frequency neural activity and human cognition: Past, present and possible future of intracranial EEG research. Prog. Neurobiol. 98, 279–301 (2012).

5. Kapeller, C. et al. CortiQ-based Real-Time Functional Mapping for Epilepsy Surgery: J. Clin. Neurophysiol. 32, e12–e22 (2015).

6. Ogawa, H. et al. Rapid and Minimum Invasive Functional Brain Mapping by Real-Time Visualization of High Gamma Activity During Awake Craniotomy. World Neurosurg. 82, 912.e1–912.e10 (2014).

7. Taplin, A. M. et al. Intraoperative Mapping of Expressive Language Cortex Using Passive Real-Time Electrocorticography. Epilepsy Behav. Case Rep. (2016). doi:10.1016/ j.ebcr.2016.03.003

8. Brunner, P. et al. A practical procedure for real-time functional mapping of eloquent cortex using electrocorticographic signals in humans. Epilepsy Behav. 15, 278–286 (2009).

9. Roland, J., Brunner, P., Johnston, J., Schalk, G. & Leuthardt, E. C. Passive real-time identification of speech and motor cortex during an awake craniotomy. Epilepsy Behav. 18, 123–128 (2010).

#Publications "Publications"



Brain Regions

Motor Function


Somatosensory System


Receptive Language


Expressive Language


Auditory System


Visual System


Visual System


Visual System


Face Recognition/Place Area


Face Recognition/Place Area


Memory Function


Memory Function


Intra Operative Monitoring
Epilepsy Neuro Monitoring (Bedside)

cortiQ related functional mapping and real-time feedback

Functional Brain Mapping with ECoG
Functional Brain Mapping with ECS
Functional Brain Mapping with fMRI
Real-time Feedback Application or BCI


Swift, J.R., Coon, W.G., Guger, C., Brunner, P., Bunch, M., Lynch, T., Frawley, B., Ritaccio, A.L. and Schalk, G., 2018. Passive Functional Mapping of Receptive Language Areas Using Electrocorticographic Signals. Clinical Neurophysiology.
Kapeller, C., Ogawa, H., Schalk, G., Kunii, N., Coon, W.G., Scharinger, J., Guger, C. and Kamada, K., 2018. Real-Time Detection and Discrimination of Visual Perception Using Electrocorticographic Signals. Journal of Neural Engineering, 15(3), 036001.

Schalk, G., Kapeller, C., Guger, C., Ogawa, H., Hiroshima, S., Lafer-Sousa, R., Saygin, Z.M., Kamada, K. and Kanwisher, N., 2017. Facephenes and rainbows: Causal evidence for functional and anatomical specificity of face and color processing in the human brain. Proceedings of the National Academy of Sciences, p.201713447.

Ogawa H, Kamada K, Kapeller C, Prueckl R, Takeuchi F, Hiroshima S, Anei R, Guger G, Clinical Impact and Implication of Real-Time Oscillation Analysis for Language Mapping, World Neurosurgery, Available online 28 September 2016, ISSN 1878-8750

Tamura Y, Ogawa H, Kapeller C, Prueckl R, Takeuchi F, Anei R, Ritaccio A, Guger C, Kamada K, Passive language mapping combining real-time oscillation analysis with cortico-cortical evoked potentials for awake craniotomy. 2016, Journal of Neurosurgery, 1.

Ritaccio, A., Matsumoto, R., Morrell, M., Kamada, K., Koubeissi, M., Poeppel, D., ... & Schalk, G. (2015). Proceedings of the Seventh International Workshop on Advances in Electrocorticography. Epilepsy & Behavior, 51, 312-320.

Christoph Kapeller (2015): Online Control of a Humanoid Robot through Hand Movement Imagination using CSP and ECoG based Features. Presentation.

Kapeller C, Korostenskaja M, Prueckl R, Chen PC, Lee KH, Westerveld M, Salinas CM, Cook JC, Baumgartner JE, Guger C., CortiQ-based Real-Time Functional Mapping for Epilepsy Surgery. J Clin Neurophysiol. 2015 Jun;32(3):e12-22. doi: 10.1097/WNP.0000000000000131

Kapeller C, Kamada K, Ogawa H, Prückl R, Kunii N, Schnürer A, Guger C. P87. Expressive and receptive language mapping using ECoG and ECS. Clinical Neurophysiology. 2015 Aug 31;126(8):e146.

Kapeller C, Schneider C, Kamada K, Ogawa H, Kunii N, Ortner R, Prückl R, Guger C. Single trial detection of hand poses in human ECoG using CSP based feature extraction. In2014 36th Annual International Conference of the IEEE Engineering in Medicine and Biology Society 2014 Aug 26 (pp. 4599-4602). IEEE.

Kapeller, C., Kamada, K., Ogawa, H., Prueckl, R., Scharinger, J., & Guger, C. (2014). An electrocorticographic BCI using code-based VEP for control in video applications: a single-subject study. Frontiers in systems neuroscience, 8.

Prueckl, R., et al. "Real-Time Software for Functional Mapping of Eloquent Cortex Using Electrocorticography." Biomedical Engineering/Biomedizinische Technik (2013).

Roland, Jarod, et al. "Passive real-time identification of speech and motor cortex during an awake craniotomy." Epilepsy & Behavior 18.1 (2010): 123-128.

Kapeller, Christoph; Kamada, Kyousuke; Ogawa, Hiroshi; Kunii, Naoto; Prueckl, Robert; Kawai, Kensuke; Schalk, Gerwin; Guger, Christoph. Comparison of ECoG and ECS Language Mapping with High-Density Electrodes. 2013 IEEE Neural Engineering Short Papers No. 0521.

Prueckl R, Kapeller C, Potes C, Korostenskaja M, Schalk G, Lee KH, Guger C., CortiQ - clinical software for electrocorticographic real-time functional mapping of the eloquent cortex. Conf Proc IEEE Eng Med Biol Soc. 2013;2013:6365-8. doi: 10.1109/EMBC.2013.6611010.

Korostenskaja, Milena, et al. "Real-Time Functional Mapping With Electrocorticography in Pediatric Epilepsy Comparison With fMRI and ESM Findings." Clinical EEG and neuroscience 45.3 (2014): 205-211.

Kamada K, Ogawa H, Kapeller C, Prueckl R, Guger C., Rapid and low-invasive functional brain mapping by realtime visualization of high gamma activity for awake craniotomy. Conf Proc IEEE Eng Med Biol Soc. 2014;2014:6802-5. doi: 10.1109/EMBC.2014.6945190.

Ogawa H, Kamada K, Kapeller C, Hiroshima S, Prueckl R, Guger C., Rapid and minimum invasive functional brain mapping by real-time visualization of high gamma activity during awake craniotomy. World Neurosurg. 2014 Nov;82(5):912.e1-10. doi: 10.1016/j.wneu.2014.08.009. Epub 2014 Aug 7. PMID: 25108295.

Brunner, Peter, et al. "A practical procedure for real-time functional mapping of eloquent cortex using electrocorticographic signals in humans." Epilepsy & Behavior 15.3 (2009): 278-286.

G. Schalk, E. C. Leuthardt, P. Brunner, J. G. Ojemann, L. A. Gerhardt, J. R. Wolpaw, Real-time detection of event-related brain activity, Neuroimage 43 (2) (2008) 245–249.

#Measurement-Results "Measurement Results"

Measurement Results


Localization of the receptive and expressive language region on the cortex

Location: University of Tokyo, Japan

Reference: Kapeller, C., Kamada, K., Ogawa, H., Prückl, R., Kunii, N., Schnürer, A., & Guger, C. (2015). P87. Expressive and receptive language mapping using ECoG and ECS. Clinical Neurophysiology, 126(8), e146.

The study included ECS and ECoG mapping with an epileptic patient with 236 subdural electrodes who underwent neuro-monitoring. The receptive and expressive language areas were each covered by a high-density subdural electrode grid with inter-electrode distance of 5 mm and conductive area of 1.5 mm. The ECoG mapping was performed with the real-time mapping system cortiQ (g.tec, Austria), which detects task related changes of gamma-band oscillations3. In order to activate the expressive language area, a picture naming task was performed during both mapping procedures. Additionally, a listening task was performed during the cortiQ mapping, to activate the receptive language area. The cortiQ mapping was repeated two times to ensure stable mapping results.


Fig 01
Figure 1: Receptive language mapping results of the ECoG mapping (Run 1 and Run 2) and the ECS mapping
Fig 02
Figure 2: Expressive language mapping results of the ECoG mapping (Run 1 and Run 2) and the ECS mapping.

Localization of the hand motor region on the cortex

Location: Asahikawa Medical University, Japan

Reference: A Case Study on Functional Brain Mapping:  Comparison ECoG, ECS and fMRI based Mapping Techniques, Not published - presented at OHBM 2014 (Poster 2190)

In this work, we used a new system for real-time functional mapping based on task-related gamma-band oscillations (cortiQ, g.tec, Austria) related to the work in67. The system identifies distinct cortical areas within a short time frame. Better yet, the patient can perform tasks voluntarily, instead of feeling externally forced to perform behavior triggered by ECS. The study included fMRI, ECS and cortiQ mapping of a patient with epilepsy having 100 subdural electrodes that underwent neuro-monitoring. The right frontal, temporal, parietal, and occipital lobes, as well as the right temporal base, were covered by standard electrode grids and strips with inter-electrode distances of 10 mm and a conductive area of ~9.4 mm². A grasping task was performed to identify the motor areas with cortiQ. A finger tapping task was used for the fMRI investigation, and the brain areas were also investigated with ECS. However, only 8 electrode sites could be tested with ECS, since ECS triggered an accidental seizure.


Fig 01
Figure 3: Merged cortiQ and fMRI result. The red circles with the yellow rings, as well as the blue area, indicate the significant activation. ECS results are highlighted with colored circles and merged with the fMRI result.

Localization of the sensorimotor and receptive language region on the cortex

Location: Florida Hospital for Children, Orland, USA

Reference: Kapeller, C., Korostenskaja, M., Prueckl, R., Chen, P. C., Lee, K. H., Westerveld, M., ... & Guger, C. (2015). CortiQ-based Real-Time Functional Mapping for Epilepsy Surgery. Journal of clinical neurophysiology, 32(3), e12-e22.

Functional magnetic resonance imaging, ESM, and cortiQ were used to determine localization of eloquent motor, sensory, and language cortex. The patient sat in front of a screen and was instructed to relax and remain as still as possible before the paradigm was started. After setup and investigation of raw data, the mapping session started. To identify particular functional regions over the cortex, the patient had to follow the instructions presented on a monitor. Specifically, we wanted to explore the motor and somatosensory area of the left hand, as well as the receptive language area (Wernicke’s). The patients went through a paradigm that consisted of 4 tasks: (1) stick out the tongue, (2) open/close the left hand, (3) feel tactile stimuli (presented via a brush) that were applied to the palm and inner side of the Fingers of the left hand, and (4) a speech comprehension task where the patient listened to a story. After an initial delay of 10 seconds, where no data were collected for analysis, the paradigm started with a 15-second baseline period, in which the instruction for the patient presented on the display was “relax”. Each task was repeated three times.


Fig 04
Figure 4: cortiQ results for multiple tasks. The mapping quality index (MQI) shows mapping quality.
Fig 05

Figure 5: ECS and fMRI result on a reconstructed brain model based on co-registered pre-operative MRI and post-operative CT.

#Advisory-Board "Advisory-Board"

Advisory Board

The mission is to provide the most accurate, reliable and quick functional mapping system to minimize the burden for patients and for neurosurgeons.



Kyosuke Kamada, MD, PhD

Asahikawa Medical University, Japan



Milena Korostenskaja, PhD

Florida Hospital for Children, US



Gerwin Schalk, PhD

Albany Medical Center and Wadsworth Research Center, USA




Anthony Ritaccio, MD

Albany Medical Center, Albany New York, USA




Adam Hebb, MD, PhD

Swedish Medical Center, USA



Kai Miller, PhD

Stanford University, USA