%0 Journal Article %J J Neurosurg Pediatr %D 2014 %T Real-time functional mapping: potential tool for improving language outcome in pediatric epilepsy surgery. %A Korostenskaja, Milena %A Chen, Po-Ching %A Salinas, Christine M %A Westerveld, Michael %A Peter Brunner %A Gerwin Schalk %A Cook, Jane C %A Baumgartner, James %A Lee, Ki H %K Adolescent %K Anticonvulsants %K Brain Mapping %K Cerebral Cortex %K Electric Stimulation %K Electroencephalography %K Epilepsies, Partial %K Female %K Humans %K Language %K Neuropsychological Tests %K Sensitivity and Specificity %K Speech %X

Accurate language localization expands surgical treatment options for epilepsy patients and reduces the risk of postsurgery language deficits. Electrical cortical stimulation mapping (ESM) is considered to be the clinical gold standard for language localization. While ESM affords clinically valuable results, it can be poorly tolerated by children, requires active participation and compliance, carries a risk of inducing seizures, is highly time consuming, and is labor intensive. Given these limitations, alternative and/or complementary functional localization methods such as analysis of electrocorticographic (ECoG) activity in high gamma frequency band in real time are needed to precisely identify eloquent cortex in children. In this case report, the authors examined 1) the use of real-time functional mapping (RTFM) for language localization in a high gamma frequency band derived from ECoG to guide surgery in an epileptic pediatric patient and 2) the relationship of RTFM mapping results to postsurgical language outcomes. The authors found that RTFM demonstrated relatively high sensitivity (75%) and high specificity (90%) when compared with ESM in a "next-neighbor" analysis. While overlapping with ESM in the superior temporal region, RTFM showed a few other areas of activation related to expressive language function, areas that were eventually resected during the surgery. The authors speculate that this resection may be associated with observed postsurgical expressive language deficits. With additional validation in more subjects, this finding would suggest that surgical planning and associated assessment of the risk/benefit ratio would benefit from information provided by RTFM mapping.

%B J Neurosurg Pediatr %V 14 %P 287-95 %8 09/2014 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/24995815 %N 3 %R 10.3171/2014.6.PEDS13477 %0 Journal Article %J J Neural Eng %D 2011 %T Decoding vowels and consonants in spoken and imagined words using electrocorticographic signals in humans. %A Pei, Xiao-Mei %A Barbour, Dennis L %A Leuthardt, E C %A Gerwin Schalk %K Adolescent %K Adult %K Brain %K Brain Mapping %K Cerebral Cortex %K Communication Aids for Disabled %K Data Interpretation, Statistical %K Discrimination (Psychology) %K Electrodes, Implanted %K Electroencephalography %K Epilepsy %K Female %K Functional Laterality %K Humans %K Male %K Middle Aged %K Movement %K Speech Perception %K User-Computer Interface %X

Several stories in the popular media have speculated that it may be possible to infer from the brain which word a person is speaking or even thinking. While recent studies have demonstrated that brain signals can give detailed information about actual and imagined actions, such as different types of limb movements or spoken words, concrete experimental evidence for the possibility to 'read the mind', i.e. to interpret internally-generated speech, has been scarce. In this study, we found that it is possible to use signals recorded from the surface of the brain (electrocorticography) to discriminate the vowels and consonants embedded in spoken and in imagined words, and we defined the cortical areas that held the most information about discrimination of vowels and consonants. The results shed light on the distinct mechanisms associated with production of vowels and consonants, and could provide the basis for brain-based communication using imagined speech.

%B J Neural Eng %V 8 %P 046028 %8 08/2011 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/21750369 %N 4 %R 10.1088/1741-2560/8/4/046028 %0 Journal Article %J J Neurosci %D 2011 %T Nonuniform high-gamma (60-500 Hz) power changes dissociate cognitive task and anatomy in human cortex. %A Charles M Gaona %A Sharma, Mohit %A Zachary V. Freudenberg %A Breshears, Jonathan %A Bundy, David T %A Roland, Jarod %A Barbour, Dennis L %A Gerwin Schalk %A Leuthardt, E C %K Acoustic Stimulation %K Adolescent %K Adult %K Analysis of Variance %K Brain Mapping %K Brain Waves %K Cerebral Cortex %K Cognition Disorders %K Electroencephalography %K Epilepsy %K Evoked Potentials %K Female %K Humans %K Male %K Middle Aged %K Neuropsychological Tests %K Nonlinear Dynamics %K Photic Stimulation %K Reaction Time %K Spectrum Analysis %K Time Factors %K Vocabulary %X

High-gamma-band (>60 Hz) power changes in cortical electrophysiology are a reliable indicator of focal, event-related cortical activity. Despite discoveries of oscillatory subthreshold and synchronous suprathreshold activity at the cellular level, there is an increasingly popular view that high-gamma-band amplitude changes recorded from cellular ensembles are the result of asynchronous firing activity that yields wideband and uniform power increases. Others have demonstrated independence of power changes in the low- and high-gamma bands, but to date, no studies have shown evidence of any such independence above 60 Hz. Based on nonuniformities in time-frequency analyses of electrocorticographic (ECoG) signals, we hypothesized that induced high-gamma-band (60-500 Hz) power changes are more heterogeneous than currently understood. Using single-word repetition tasks in six human subjects, we showed that functional responsiveness of different ECoG high-gamma sub-bands can discriminate cognitive task (e.g., hearing, reading, speaking) and cortical locations. Power changes in these sub-bands of the high-gamma range are consistently present within single trials and have statistically different time courses within the trial structure. Moreover, when consolidated across all subjects within three task-relevant anatomic regions (sensorimotor, Broca's area, and superior temporal gyrus), these behavior- and location-dependent power changes evidenced nonuniform trends across the population. Together, the independence and nonuniformity of power changes across a broad range of frequencies suggest that a new approach to evaluating high-gamma-band cortical activity is necessary. These findings show that in addition to time and location, frequency is another fundamental dimension of high-gamma dynamics.

%B J Neurosci %V 31 %P 2091-100 %8 02/2011 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/21307246 %N 6 %R 10.1523/JNEUROSCI.4722-10.2011 %0 Journal Article %J Proc Natl Acad Sci U S A %D 2010 %T Cortical activity during motor execution, motor imagery, and imagery-based online feedback. %A Miller, K.J. %A Gerwin Schalk %A Fetz, Eberhard E %A den Nijs, Marcel %A Ojemann, J G %A Rao, Rajesh P N %K Adolescent %K Adult %K Biofeedback, Psychology %K Cerebral Cortex %K Child %K Electric Stimulation %K Electrocardiography %K Female %K Humans %K Male %K Middle Aged %K Motor Activity %K Young Adult %X

Imagery of motor movement plays an important role in learning of complex motor skills, from learning to serve in tennis to perfecting a pirouette in ballet. What and where are the neural substrates that underlie motor imagery-based learning? We measured electrocorticographic cortical surface potentials in eight human subjects during overt action and kinesthetic imagery of the same movement, focusing on power in "high frequency" (76-100 Hz) and "low frequency" (8-32 Hz) ranges. We quantitatively establish that the spatial distribution of local neuronal population activity during motor imagery mimics the spatial distribution of activity during actual motor movement. By comparing responses to electrocortical stimulation with imagery-induced cortical surface activity, we demonstrate the role of primary motor areas in movement imagery. The magnitude of imagery-induced cortical activity change was approximately 25% of that associated with actual movement. However, when subjects learned to use this imagery to control a computer cursor in a simple feedback task, the imagery-induced activity change was significantly augmented, even exceeding that of overt movement.

%B Proc Natl Acad Sci U S A %V 107 %P 4430-5 %8 03/2010 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/20160084 %N 9 %R 10.1073/pnas.0913697107 %0 Journal Article %J Neurosurgery %D 2010 %T Electrocorticographic frequency alteration mapping for extraoperative localization of speech cortex. %A Wu, Melinda %A Wisneski, Kimberly %A Gerwin Schalk %A Sharma, Mohit %A Roland, Jarod %A Breshears, Jonathan %A Charles M Gaona %A Leuthardt, E C %K Acoustic Stimulation %K Adolescent %K Adult %K Brain Mapping %K Cerebral Cortex %K Chi-Square Distribution %K Electroencephalography %K Epilepsy %K Female %K Humans %K Male %K Mass Spectrometry %K Middle Aged %K Photic Stimulation %K Speech %K Verbal Behavior %K Young Adult %X

OBJECTIVE: 

Electrocortical stimulation (ECS) has long been established for delineating eloquent cortex in extraoperative mapping. However, ECS is still coarse and inefficient in delineating regions of functional cortex and can be hampered by afterdischarges. Given these constraints, an adjunct approach to defining motor cortex is the use of electrocorticographic (ECoG) signal changes associated with active regions of cortex. The broad range of frequency oscillations are categorized into 2 main groups with respect to sensorimotor cortex: low-frequency bands (LFBs) and high-frequency bands (HFBs). The LFBs tend to show a power reduction, whereas the HFBs show power increases with cortical activation. These power changes associated with activated cortex could potentially provide a powerful tool in delineating areas of speech cortex. We explore ECoG signal alterations as they occur with activated region of speech cortex and its potential in clinical brain mapping applications.

METHODS: 

We evaluated 7 patients who underwent invasive monitoring for seizure localization. Each had extraoperative ECS mapping to identify speech cortex. Additionally, all subjects performed overt speech tasks with an auditory or a visual cue to identify associated frequency power changes in regard to location and degree of concordance with ECS results.

RESULTS: 

Electrocorticographic frequency alteration mapping (EFAM) had an 83.9% sensitivity and a 40.4% specificity in identifying any language site when considering both frequency bands and both stimulus cues. Electrocorticographic frequency alteration mapping was more sensitive in identifying the Wernicke area (100%) than the Broca area (72.2%). The HFB is uniquely suited to identifying the Wernicke area, whereas a combination of the HFB and LFB is important for Broca localization.

CONCLUSION: 

The concordance between stimulation and spectral power changes demonstrates the possible utility of EFAM as an adjunct method to improve the efficiency and resolution of identifying speech cortex.

%B Neurosurgery %V 66 %P E407-9 %8 02/2010 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/20087111 %N 2 %R 10.1227/01.NEU.0000345352.13696.6F %0 Journal Article %J Epilepsy Behav %D 2010 %T Passive real-time identification of speech and motor cortex during an awake craniotomy. %A Roland, Jarod %A Peter Brunner %A Johnston, James %A Gerwin Schalk %A Leuthardt, E C %K Brain Mapping %K Brain Neoplasms %K Cerebral Cortex %K Craniotomy %K Electric Stimulation %K Electroencephalography %K Humans %K Neurologic Examination %X

Precise localization of eloquent cortex is a clinical necessity prior to surgical resections adjacent to speech or motor cortex. In the intraoperative setting, this traditionally requires inducing temporary lesions by direct electrocortical stimulation (DECS). In an attempt to increase efficiency and potentially reduce the amount of necessary stimulation, we used a passive mapping procedure in the setting of an awake craniotomy for tumor in two patients resection. We recorded electrocorticographic (ECoG) signals from exposed cortex while patients performed simple cue-directed motor and speech tasks. SIGFRIED, a procedure for real-time event detection, was used to identify areas of cortical activation by detecting task-related modulations in the ECoG high gamma band. SIGFRIED's real-time output quickly localized motor and speech areas of cortex similar to those identified by DECS. In conclusion, real-time passive identification of cortical function using SIGFRIED may serve as a useful adjunct to cortical stimulation mapping in the intraoperative setting.

%B Epilepsy Behav %V 18 %P 123-8 %8 05/2010 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/20478745 %N 1-2 %R 10.1016/j.yebeh.2010.02.017 %0 Journal Article %J Neurosurg Focus %D 2009 %T Evolution of brain-computer interfaces: going beyond classic motor physiology. %A Leuthardt, E C %A Gerwin Schalk %A Roland, Jarod %A Rouse, Adam %A Moran, D %K Brain %K Cerebral Cortex %K Humans %K Man-Machine Systems %K Motor Cortex %K Movement %K Movement Disorders %K Neuronal Plasticity %K Prostheses and Implants %K Research %K Signal Processing, Computer-Assisted %K User-Computer Interface %X

The notion that a computer can decode brain signals to infer the intentions of a human and then enact those intentions directly through a machine is becoming a realistic technical possibility. These types of devices are known as brain-computer interfaces (BCIs). The evolution of these neuroprosthetic technologies could have significant implications for patients with motor disabilities by enhancing their ability to interact and communicate with their environment. The cortical physiology most investigated and used for device control has been brain signals from the primary motor cortex. To date, this classic motor physiology has been an effective substrate for demonstrating the potential efficacy of BCI-based control. However, emerging research now stands to further enhance our understanding of the cortical physiology underpinning human intent and provide further signals for more complex brain-derived control. In this review, the authors report the current status of BCIs and detail the emerging research trends that stand to augment clinical applications in the future.

%B Neurosurg Focus %V 27 %P E4 %8 07/2009 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/19569892 %N 1 %R 10.3171/2009.4.FOCUS0979 %0 Journal Article %J Epilepsy Behav %D 2009 %T A practical procedure for real-time functional mapping of eloquent cortex using electrocorticographic signals in humans. %A Peter Brunner %A A L Ritaccio %A Lynch, Timothy M %A Emrich, Joseph F %A Adam J Wilson %A Williams, Justin C %A Aarnoutse, Erik J %A Ramsey, Nick F %A Leuthardt, E C %A H Bischof %A Gerwin Schalk %K Adult %K Brain Mapping %K Cerebral Cortex %K Electric Stimulation %K Electrodes, Implanted %K Electroencephalography %K Epilepsy %K Female %K Humans %K Male %K Middle Aged %K Practice Guidelines as Topic %K Signal Processing, Computer-Assisted %K Young Adult %X

Functional mapping of eloquent cortex is often necessary prior to invasive brain surgery, but current techniques that derive this mapping have important limitations. In this article, we demonstrate the first comprehensive evaluation of a rapid, robust, and practical mapping system that uses passive recordings of electrocorticographic signals. This mapping procedure is based on the BCI2000 and SIGFRIED technologies that we have been developing over the past several years. In our study, we evaluated 10 patients with epilepsy from four different institutions and compared the results of our procedure with the results derived using electrical cortical stimulation (ECS) mapping. The results show that our procedure derives a functional motor cortical map in only a few minutes. They also show a substantial concurrence with the results derived using ECS mapping. Specifically, compared with ECS maps, a next-neighbor evaluation showed no false negatives, and only 0.46 and 1.10% false positives for hand and tongue maps, respectively. In summary, we demonstrate the first comprehensive evaluation of a practical and robust mapping procedure that could become a new tool for planning of invasive brain surgeries.

%B Epilepsy Behav %V 15 %P 278-86 %8 07/2009 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/19366638 %N 3 %R 10.1016/j.yebeh.2009.04.001 %0 Journal Article %J J Neurosci %D 2008 %T Advanced neurotechnologies for chronic neural interfaces: new horizons and clinical opportunities. %A Kipke, Daryl R %A Shain, William %A Buzsáki, György %A Fetz, Eberhard E %A Henderson, Jaimie M %A Hetke, Jamille F %A Gerwin Schalk %K Cerebral Cortex %K Electrodes, Implanted %K Electroencephalography %K Electronics, Medical %K Electrophysiology %K Evoked Potentials %K Movement Disorders %K Neurons %K Prostheses and Implants %K User-Computer Interface %B J Neurosci %V 28 %P 11830-8 %8 11/2008 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/19005048?report=abstract %N 46 %R 10.1523/JNEUROSCI.3879-08.2008 %0 Journal Article %J J Neural Eng %D 2007 %T Decoding two-dimensional movement trajectories using electrocorticographic signals in humans. %A Gerwin Schalk %A Kubánek, J %A Miller, John W %A Nicholas R Anderson %A Leuthardt, E C %A Ojemann, J G %A Limbrick, D %A Moran, D %A Lester A Gerhardt %A Jonathan Wolpaw %K Adult %K Algorithms %K Arm %K Brain Mapping %K Cerebral Cortex %K Electroencephalography %K Evoked Potentials, Motor %K Female %K Humans %K Male %K Movement %X

Signals from the brain could provide a non-muscular communication and control system, a brain-computer interface (BCI), for people who are severely paralyzed. A common BCI research strategy begins by decoding kinematic parameters from brain signals recorded during actual arm movement. It has been assumed that these parameters can be derived accurately only from signals recorded by intracortical microelectrodes, but the long-term stability of such electrodes is uncertain. The present study disproves this widespread assumption by showing in humans that kinematic parameters can also be decoded from signals recorded by subdural electrodes on the cortical surface (ECoG) with an accuracy comparable to that achieved in monkey studies using intracortical microelectrodes. A new ECoG feature labeled the local motor potential (LMP) provided the most information about movement. Furthermore, features displayed cosine tuning that has previously been described only for signals recorded within the brain. These results suggest that ECoG could be a more stable and less invasive alternative to intracortical electrodes for BCI systems, and could also prove useful in studies of motor function.

%B J Neural Eng %V 4 %P 264-75 %8 09/2007 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/17873429 %N 3 %R 10.1088/1741-2560/4/3/012 %0 Journal Article %J IEEE Trans Biomed Eng %D 2007 %T A µ-rhythm Matched Filter for Continuous Control of a Brain-Computer Interface. %A Krusienski, Dean J %A Gerwin Schalk %A Dennis J. McFarland %A Jonathan Wolpaw %K Algorithms %K Cerebral Cortex %K Cortical Synchronization %K Electroencephalography %K Evoked Potentials %K Humans %K Imagination %K Pattern Recognition, Automated %K User-Computer Interface %X

A brain-computer interface (BCI) is a system that provides an alternate nonmuscular communication/control channel for individuals with severe neuromuscular disabilities. With proper training, individuals can learn to modulate the amplitude of specific electroencephalographic (EEG) components (e.g., the 8-12 Hz mu rhythm and 18-26 Hz beta rhythm) over the sensorimotor cortex and use them to control a cursor on a computer screen. Conventional spectral techniques for monitoring the continuousamplitude fluctuations fail to capture essential amplitude/phase relationships of the mu and beta rhythms in a compact fashion and, therefore, are suboptimal. By extracting the characteristic mu rhythm for a user, the exact morphology can be characterized and exploited as a matched filter. A simple, parameterized model for the characteristic mu rhythm is proposed and its effectiveness as a matched filter is examined online for a one-dimensional cursor control task. The results suggest that amplitude/phase coupling exists between the mu and beta bands during event-related desynchronization, and that an appropriate matched filter can provide improved performance.

%B IEEE Trans Biomed Eng %V 54 %P 273-80 %8 02/2007 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/17278584 %N 2 %R 10.1109/TBME.2006.886661 %0 Journal Article %J IEEE Trans Neural Syst Rehabil Eng %D 2006 %T ECoG factors underlying multimodal control of a brain-computer interface. %A Adam J Wilson %A Felton, Elizabeth A %A Garell, P Charles %A Gerwin Schalk %A Williams, Justin C %K Adult %K Brain Mapping %K Cerebral Cortex %K Communication Aids for Disabled %K Computer Peripherals %K Evoked Potentials %K Female %K Humans %K Imagination %K Male %K Man-Machine Systems %K Neuromuscular Diseases %K Systems Integration %K User-Computer Interface %K Volition %X

Most current brain-computer interface (BCI) systems for humans use electroencephalographic activity recorded from the scalp, and may be limited in many ways. Electrocorticography (ECoG) is believed to be a minimally-invasive alternative to electroencephalogram (EEG) for BCI systems, yielding superior signal characteristics that could allow rapid user training and faster communication rates. In addition, our preliminary results suggest that brain regions other than the sensorimotor cortex, such as auditory cortex, may be trained to control a BCI system using similar methods as those used to train motor regions of the brain. This could prove to be vital for users who have neurological disease, head trauma, or other conditions precluding the use of sensorimotor cortex for BCI control.

%B IEEE Trans Neural Syst Rehabil Eng %V 14 %P 246-50 %8 06/2006 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/16792305 %N 2 %R 10.1109/TNSRE.2006.875570 %0 Journal Article %J IEEE Trans Neural Syst Rehabil Eng %D 2006 %T Electrocorticography-based brain computer interface--the Seattle experience. %A Leuthardt, E C %A Miller, John W %A Gerwin Schalk %A Rao, Rajesh P N %A Ojemann, J G %K Cerebral Cortex %K Electroencephalography %K Epilepsy %K Evoked Potentials %K Humans %K Therapy, Computer-Assisted %K User-Computer Interface %K Washington %X

Electrocorticography (ECoG) has been demonstrated to be an effective modality as a platform for brain-computer interfaces (BCIs). Through our experience with ten subjects, we further demonstrate evidence to support the power and flexibility of this signal for BCI usage. In a subset of four patients, closed-loop BCI experiments were attempted with the patient receiving online feedback that consisted of one-dimensional cursor movement controlled by ECoG features that had shown correlation with various real and imagined motor and speech tasks. All four achieved control, with final target accuracies between 73%-100%. We assess the methods for achieving control and the manner in which enhancing online control can be accomplished by rescreening during online tasks. Additionally, we assess the relevant issues of the current experimental paradigm in light of their clinical constraints.

%B IEEE Trans Neural Syst Rehabil Eng %V 14 %P 194-8 %8 06/2006 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/16792292 %N 2 %R 10.1109/TNSRE.2006.875536 %0 Journal Article %J IEEE Trans Rehabil Eng %D 2000 %T Brain-computer interface technology: a review of the first international meeting. %A Jonathan Wolpaw %A Niels Birbaumer %A Heetderks, W J %A Dennis J. McFarland %A Peckham, P H %A Gerwin Schalk %A Emanuel Donchin %A Quatrano, L A %A Robinson, C J %A Theresa M Vaughan %K Algorithms %K Cerebral Cortex %K Communication Aids for Disabled %K Disabled Persons %K Electroencephalography %K Evoked Potentials %K Humans %K Neuromuscular Diseases %K Signal Processing, Computer-Assisted %K User-Computer Interface %X

Over the past decade, many laboratories have begun to explore brain-computer interface (BCI) technology as a radically new communication option for those with neuromuscular impairments that prevent them from using conventional augmentative communication methods. BCI's provide these users with communication channels that do not depend on peripheral nerves and muscles. This article summarizes the first international meeting devoted to BCI research and development. Current BCI's use electroencephalographic (EEG) activity recorded at the scalp or single-unit activity recorded from within cortex to control cursor movement, select letters or icons, or operate a neuroprosthesis. The central element in each BCI is a translation algorithm that converts electrophysiological input from the user into output that controls external devices. BCI operation depends on effective interaction between two adaptive controllers, the user who encodes his or her commands in the electrophysiological input provided to the BCI, and the BCI which recognizes the commands contained in the input and expresses them in device control. Current BCI's have maximum information transfer rates of 5-25 b/min. Achievement of greater speed and accuracy depends on improvements in signal processing, translation algorithms, and user training. These improvements depend on increased interdisciplinary cooperation between neuroscientists, engineers, computer programmers, psychologists, and rehabilitation specialists, and on adoption and widespread application of objective methods for evaluating alternative methods. The practical use of BCI technology depends on the development of appropriate applications, identification of appropriate user groups, and careful attention to the needs and desires of individual users. BCI research and development will also benefit from greater emphasis on peer-reviewed publications, and from adoption of standard venues for presentations and discussion.

%B IEEE Trans Rehabil Eng %V 8 %P 164-73 %8 06/2000 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/10896178 %N 2 %R 10.1109/TRE.2000.847807