%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 Neuroimage %D 2011 %T Spatiotemporal dynamics of electrocorticographic high gamma activity during overt and covert word repetition. %A Pei, Xiao-Mei %A Leuthardt, E C %A Charles M Gaona %A Peter Brunner %A Jonathan Wolpaw %A Gerwin Schalk %K Adolescent %K Adult %K Brain %K Brain Mapping %K Electroencephalography %K Female %K Humans %K Male %K Middle Aged %K Signal Processing, Computer-Assisted %K Verbal Behavior %X

Language is one of the defining abilities of humans. Many studies have characterized the neural correlates of different aspects of language processing. However, the imaging techniques typically used in these studies were limited in either their temporal or spatial resolution. Electrocorticographic (ECoG) recordings from the surface of the brain combine high spatial with high temporal resolution and thus could be a valuable tool for the study of neural correlates of language function. In this study, we defined the spatiotemporal dynamics of ECoG activity during a word repetition task in nine human subjects. ECoG was recorded while each subject overtly or covertly repeated words that were presented either visually or auditorily. ECoG amplitudes in the high gamma (HG) band confidently tracked neural changes associated with stimulus presentation and with the subject's verbal response. Overt word production was primarily associated with HG changes in the superior and middle parts of temporal lobe, Wernicke's area, the supramarginal gyrus, Broca's area, premotor cortex (PMC), primary motor cortex. Covert word production was primarily associated with HG changes in superior temporal lobe and the supramarginal gyrus. Acoustic processing from both auditory stimuli as well as the subject's own voice resulted in HG power changes in superior temporal lobe and Wernicke's area. In summary, this study represents a comprehensive characterization of overt and covert speech using electrophysiological imaging with high spatial and temporal resolution. It thereby complements the findings of previous neuroimaging studies of language and thus further adds to current understanding of word processing in humans.

%B Neuroimage %V 54 %P 2960-72 %8 02/2011 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/21029784 %N 4 %R 10.1016/j.neuroimage.2010.10.029 %0 Journal Article %J J Neural Eng %D 2011 %T Using the electrocorticographic speech network to control a brain-computer interface in humans. %A Leuthardt, E C %A Charles M Gaona %A Sharma, Mohit %A Szrama, Nicholas %A Roland, Jarod %A Zachary V. Freudenberg %A Solisb, Jamie %A Breshears, Jonathan %A Gerwin Schalk %K Adult %K Brain %K Brain Mapping %K Computer Peripherals %K Electroencephalography %K Evoked Potentials %K Feedback, Physiological %K Female %K Humans %K Imagination %K Male %K Middle Aged %K Nerve Net %K Speech Production Measurement %K User-Computer Interface %X

Electrocorticography (ECoG) has emerged as a new signal platform for brain-computer interface (BCI) systems. Classically, the cortical physiology that has been commonly investigated and utilized for device control in humans has been brain signals from the sensorimotor cortex. Hence, it was unknown whether other neurophysiological substrates, such as the speech network, could be used to further improve on or complement existing motor-based control paradigms. We demonstrate here for the first time that ECoG signals associated with different overt and imagined phoneme articulation can enable invasively monitored human patients to control a one-dimensional computer cursor rapidly and accurately. This phonetic content was distinguishable within higher gamma frequency oscillations and enabled users to achieve final target accuracies between 68% and 91% within 15 min. Additionally, one of the patients achieved robust control using recordings from a microarray consisting of 1 mm spaced microwires. These findings suggest that the cortical network associated with speech could provide an additional cognitive and physiologic substrate for BCI operation and that these signals can be acquired from a cortical array that is small and minimally invasive.

%B J Neural Eng %V 8 %P 036004 %8 06/2011 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/21471638 %N 3 %R 10.1088/1741-2560/8/3/036004 %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 J Neural Eng %D 2010 %T Does the 'P300' speller depend on eye gaze?. %A Peter Brunner %A Joshi, S %A S Briskin %A Jonathan Wolpaw %A H Bischof %A Gerwin Schalk %K Adult %K Event-Related Potentials, P300 %K Eye Movements %K Female %K Humans %K Male %K Middle Aged %K Models, Neurological %K Photic Stimulation %K User-Computer Interface %K Young Adult %X

Many people affected by debilitating neuromuscular disorders such as amyotrophic lateral sclerosis, brainstem stroke or spinal cord injury are impaired in their ability to, or are even unable to, communicate. A brain-computer interface (BCI) uses brain signals, rather than muscles, to re-establish communication with the outside world. One particular BCI approach is the so-called 'P300 matrix speller' that was first described by Farwell and Donchin (1988 Electroencephalogr. Clin. Neurophysiol. 70 510-23). It has been widely assumed that this method does not depend on the ability to focus on the desired character, because it was thought that it relies primarily on the P300-evoked potential and minimally, if at all, on other EEG features such as the visual-evoked potential (VEP). This issue is highly relevant for the clinical application of this BCI method, because eye movements may be impaired or lost in the relevant user population. This study investigated the extent to which the performance in a 'P300' speller BCI depends on eye gaze. We evaluated the performance of 17 healthy subjects using a 'P300' matrix speller under two conditions. Under one condition ('letter'), the subjects focused their eye gaze on the intended letter, while under the second condition ('center'), the subjects focused their eye gaze on a fixation cross that was located in the center of the matrix. The results show that the performance of the 'P300' matrix speller in normal subjects depends in considerable measure on gaze direction. They thereby disprove a widespread assumption in BCI research, and suggest that this BCI might function more effectively for people who retain some eye-movement control. The applicability of these findings to people with severe neuromuscular disabilities (particularly in eye-movements) remains to be determined.

%B J Neural Eng %V 7 %P 056013 %8 10/2010 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/20858924 %N 5 %R 10.1088/1741-2560/7/5/056013 %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 J Neural Eng %D 2009 %T Decoding flexion of individual fingers using electrocorticographic signals in humans. %A Kubánek, J %A Miller, John W %A Ojemann, J G %A Jonathan Wolpaw %A Gerwin Schalk %K Adolescent %K Adult %K Biomechanics %K Brain %K Electrodiagnosis %K Epilepsy %K Female %K Fingers %K Humans %K Male %K Microelectrodes %K Middle Aged %K Motor Activity %K Rest %K Thumb %K Time Factors %K Young Adult %X

Brain signals can provide the basis for a non-muscular communication and control system, a brain-computer interface (BCI), for people with motor disabilities. A common approach to creating BCI devices is to decode kinematic parameters of movements using signals recorded by intracortical microelectrodes. Recent studies have shown that kinematic parameters of hand movements can also be accurately decoded from signals recorded by electrodes placed on the surface of the brain (electrocorticography (ECoG)). In the present study, we extend these results by demonstrating that it is also possible to decode the time course of the flexion of individual fingers using ECoG signals in humans, and by showing that these flexion time courses are highly specific to the moving finger. These results provide additional support for the hypothesis that ECoG could be the basis for powerful clinically practical BCI systems, and also indicate that ECoG is useful for studying cortical dynamics related to motor function.

%B J Neural Eng %V 6 %P 066001 %8 12/2009 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/19794237 %N 6 %R 10.1088/1741-2560/6/6/066001 %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 Brain Res Bull %D 2008 %T Non-invasive brain-computer interface system: towards its application as assistive technology. %A Cincotti, F %A Mattia, Donatella %A Aloise, Fabio %A Bufalari, Simona %A Gerwin Schalk %A Oriolo, Giuseppe %A Cherubini, Andrea %A Marciani, Maria Grazia %A Babiloni, Fabio %K Activities of Daily Living %K Adolescent %K Adult %K Brain %K Child %K Electroencephalography %K Evoked Potentials, Motor %K Female %K Humans %K Learning %K Male %K Middle Aged %K Motor Skills %K Muscular Dystrophy, Duchenne %K Pilot Projects %K Prostheses and Implants %K Robotics %K Self-Help Devices %K Software %K Spinal Muscular Atrophies of Childhood %K User-Computer Interface %K Volition %X

The quality of life of people suffering from severe motor disabilities can benefit from the use of current assistive technology capable of ameliorating communication, house-environment management and mobility, according to the user's residual motor abilities. Brain-computer interfaces (BCIs) are systems that can translate brain activity into signals that control external devices. Thus they can represent the only technology for severely paralyzed patients to increase or maintain their communication and control options. Here we report on a pilot study in which a system was implemented and validated to allow disabled persons to improve or recover their mobility (directly or by emulation) and communication within the surrounding environment. The system is based on a software controller that offers to the user a communication interface that is matched with the individual's residual motor abilities. Patients (n=14) with severe motor disabilities due to progressive neurodegenerative disorders were trained to use the system prototype under a rehabilitation program carried out in a house-like furnished space. All users utilized regular assistive control options (e.g., microswitches or head trackers). In addition, four subjects learned to operate the system by means of a non-invasive EEG-based BCI. This system was controlled by the subjects' voluntary modulations of EEG sensorimotor rhythms recorded on the scalp; this skill was learnt even though the subjects have not had control over their limbs for a long time. We conclude that such a prototype system, which integrates several different assistive technologies including a BCI system, can potentially facilitate the translation from pre-clinical demonstrations to a clinical useful BCI.

%B Brain Res Bull %V 75 %P 796-803 %8 04/2008 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/18394526 %N 6 %R 10.1016/j.brainresbull.2008.01.007 %0 Conference Proceedings %B Conf Proc IEEE Eng Med Biol Soc %D 2008 %T Three cases of feature correlation in an electrocorticographic BCI. %A Miller, John W %A Blakely, Timothy %A Gerwin Schalk %A den Nijs, Marcel %A Rao, Rajesh P N %A Ojemann, J G %K Adolescent %K Adult %K Algorithms %K Electrocardiography %K Evoked Potentials, Motor %K Female %K Humans %K Male %K Middle Aged %K Motor Cortex %K Pattern Recognition, Automated %K Statistics as Topic %K Task Performance and Analysis %K User-Computer Interface %X Three human subjects participated in a closed-loop brain computer interface cursor control experiment mediated by implanted subdural electrocorticographic arrays. The paradigm consisted of several stages: baseline recording, hand and tongue motor tasks as the basis for feature selection, two closed-loop one-dimensional feedback experiments with each of these features, and a two-dimensional feedback experiment using both of the features simultaneously. The two selected features were simple channel and frequency band combinations associated with change during hand and tongue movement. Inter-feature correlation and cross-correlation between features during different epochs of each task were quantified for each stage of the experiment. Our anecdotal, three subject, result suggests that while high correlation between horizontal and vertical control signal can initially preclude successful two-dimensional cursor control, a feedback-based learning strategy can be successfully employed by the subject to overcome this limitation and progressively decorrelate these control signals. %B Conf Proc IEEE Eng Med Biol Soc %P 5318-21 %8 2008 %G eng %R 10.1109/IEMBS.2008.4650415 %0 Conference Paper %B Engineering in Medicine and Biology Society, 2008. %D 2008 %T Three cases of feature correlation in an electrocorticographic BCI. %A Miller, Kai J %A Blakely, Timothy %A Gerwin Schalk %A den Nijs, Marcel %A Rao, Rajesh PN %A Ojemann, Jeffrey G %K Adolescent %K Adult %K Algorithms %K automated pattern recognition %K control systems %K decorrelation %K Electrocardiography %K Electrodes %K Electroencephalography %K evoked motor potentials %K Feedback %K Female %K frequency %K hospitals %K Humans %K Male %K Middle Aged %K Motor Cortex %K Signal Processing %K Statistics as Topic %K Task Performance and Analysis %K Tongue %K User-Computer Interface %X Three human subjects participated in a closed-loop brain computer interface cursor control experiment mediated by implanted subdural electrocorticographic arrays. The paradigm consisted of several stages: baseline recording, hand and tongue motor tasks as the basis for feature selection, two closed-loop one-dimensional feedback experiments with each of these features, and a two-dimensional feedback experiment using both of the features simultaneously. The two selected features were simple channel and frequency band combinations associated with change during hand and tongue movement. Inter-feature correlation and cross-correlation between features during different epochs of each task were quantified for each stage of the experiment. Our anecdotal, three subject, result suggests that while high correlation between horizontal and vertical control signal can initially preclude successful two-dimensional cursor control, a feedback-based learning strategy can be successfully employed by the subject to overcome this limitation and progressively decorrelate these control signals. %B Engineering in Medicine and Biology Society, 2008. %I IEEE %C Vancouver, BC %8 08/2008 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/19163918 %R 10.1109/IEMBS.2008.4650415 %0 Journal Article %J Stroke %D 2008 %T Unique cortical physiology associated with ipsilateral hand movements and neuroprosthetic implications. %A Wisneski, Kimberly %A Nicholas R Anderson %A Gerwin Schalk %A Smyth, Matt %A Moran, D %A Leuthardt, E C %K Adolescent %K Adult %K Artificial Limbs %K Bionics %K Brain Mapping %K Child %K Dominance, Cerebral %K Electroencephalography %K Female %K Hand %K Humans %K Male %K Middle Aged %K Motor Cortex %K Movement %K Paresis %K Prosthesis Design %K Psychomotor Performance %K Stroke %K User-Computer Interface %K Volition %X

BACKGROUND AND PURPOSE: 

Brain computer interfaces (BCIs) offer little direct benefit to patients with hemispheric stroke because current platforms rely on signals derived from the contralateral motor cortex (the same region injured by the stroke). For BCIs to assist hemiparetic patients, the implant must use unaffected cortex ipsilateral to the affected limb. This requires the identification of distinct electrophysiological features from the motor cortex associated with ipsilateral hand movements.

METHODS: 

In this study we studied 6 patients undergoing temporary placement of intracranial electrode arrays. Electrocorticographic (ECoG) signals were recorded while the subjects engaged in specific ipsilateral or contralateral hand motor tasks. Spectral changes were identified with regards to frequency, location, and timing.

RESULTS: 

Ipsilateral hand movements were associated with electrophysiological changes that occur in lower frequency spectra, at distinct anatomic locations, and earlier than changes associated with contralateral hand movements. In a subset of 3 patients, features specific to ipsilateral and contralateral hand movements were used to control a cursor on a screen in real time. In ipsilateral derived control this was optimal with lower frequency spectra.

CONCLUSIONS: 

There are distinctive cortical electrophysiological features associated with ipsilateral movements which can be used for device control. These findings have implications for patients with hemispheric stroke because they offer a potential methodology for which a single hemisphere can be used to enhance the function of a stroke induced hemiparesis.

%B Stroke %V 39 %P 3351-9 %8 12/2008 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/18927456 %N 12 %R 10.1161/STROKEAHA.108.518175 %0 Journal Article %J Neurosurgery %D 2007 %T Electrocorticographic Frequency Alteration Mapping: A Clinical Technique for Mapping the Motor Cortex. %A Leuthardt, E C %A Miller, John W %A Nicholas R Anderson %A Gerwin Schalk %A Dowling, Joshua %A Miller, John W %A Moran, D %A Ojemann, J G %K Adult %K Biological Clocks %K Brain Mapping %K Electric Stimulation %K Electrodes, Implanted %K Electroencephalography %K Female %K Hand %K Humans %K Male %K Middle Aged %K Motor Cortex %K Oscillometry %K Signal Processing, Computer-Assisted %K Tongue %X

OBJECTIVE: 

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

METHODS: 

We evaluated seven patients who underwent invasive monitoring for seizure localization. Each patient had extraoperative ECS mapping to identify the motor cortex. All patients also performed overt hand and tongue motor tasks to identify associated frequency power changes in regard to location and degree of concordance with ECS results that localized either hand or tongue motor function.

RESULTS: 

The low frequency bands had a high sensitivity (88.9-100%) and a lower specificity (79.0-82.6%) for identifying electrodes with either hand or tongue ECS motor responses. The high frequency bands had a lower sensitivity (72.7-88.9%) and a higher specificity (92.4-94.9%) in correlation with the same respective ECS positive electrodes.

CONCLUSION: 

The concordance between stimulation and spectral power changes demonstrate the possible utility of electrocorticographic frequency alteration mapping as an adjunct method to improve the efficiency and resolution of identifying the motor cortex.

%B Neurosurgery %V 60 %P 260-70; discussion 270-1 %8 04/2007 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/17415162 %N 4 Suppl 2 %R 10.1227/01.NEU.0000255413.70807.6E %0 Journal Article %J J Neurosci %D 2007 %T Spectral Changes in Cortical Surface Potentials During Motor Movement. %A Miller, John W %A Leuthardt, E C %A Gerwin Schalk %A Rao, Rajesh P N %A Nicholas R Anderson %A Moran, D %A Miller, John W %A Ojemann, J G %K Adult %K Brain Mapping %K Female %K Humans %K Male %K Middle Aged %K Motor Cortex %K Movement %X

In the first large study of its kind, we quantified changes in electrocorticographic signals associated with motor movement across 22 subjects with subdural electrode arrays placed for identification of seizure foci. Patients underwent a 5-7 d monitoring period with array placement, before seizure focus resection, and during this time they participated in the study. An interval-based motor-repetition task produced consistent and quantifiable spectral shifts that were mapped on a Talairach-standardized template cortex. Maps were created independently for a high-frequency band (HFB) (76-100 Hz) and a low-frequency band (LFB) (8-32 Hz) for several different movement modalities in each subject. The power in relevant electrodes consistently decreased in the LFB with movement, whereas the power in the HFB consistently increased. In addition, the HFB changes were more focal than the LFB changes. Sites of power changes corresponded to stereotactic locations in sensorimotor cortex and to the results of individual clinical electrical cortical mapping. Sensorimotor representation was found to be somatotopic, localized in stereotactic space to rolandic cortex, and typically followed the classic homunculus with limited extrarolandic representation.

%B J Neurosci %V 27 %P 2424-32 %8 02/2007 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/17329441 %N 9 %R 10.1523/JNEUROSCI.3886-06.2007 %0 Journal Article %J Neurology %D 2005 %T Patients with ALS can use sensorimotor rhythms to operate a brain-computer interface. %A Kübler, A. %A Nijboer, F %A Mellinger, Jürgen %A Theresa M Vaughan %A Pawelzik, H %A Gerwin Schalk %A Dennis J. McFarland %A Niels Birbaumer %A Jonathan Wolpaw %K Aged %K Amyotrophic Lateral Sclerosis %K Electroencephalography %K Evoked Potentials, Motor %K Evoked Potentials, Somatosensory %K Female %K Humans %K Imagination %K Male %K Middle Aged %K Motor Cortex %K Movement %K Paralysis %K Photic Stimulation %K Prostheses and Implants %K Somatosensory Cortex %K Treatment Outcome %K User-Computer Interface %X

People with severe motor disabilities can maintain an acceptable quality of life if they can communicate. Brain-computer interfaces (BCIs), which do not depend on muscle control, can provide communication. Four people severely disabled by ALS learned to operate a BCI with EEG rhythms recorded over sensorimotor cortex. These results suggest that a sensorimotor rhythm-based BCI could help maintain quality of life for people with ALS.

%B Neurology %V 64 %P 1775-7 %8 05/2005 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/15911809 %N 10 %R 10.1212/01.WNL.0000158616.43002.6D %0 Journal Article %J IEEE Trans Neural Syst Rehabil Eng %D 2003 %T The Wadsworth Center brain-computer interface (BCI) research and development program. %A Jonathan Wolpaw %A Dennis J. McFarland %A Theresa M Vaughan %A Gerwin Schalk %K Academic Medical Centers %K Adult %K Algorithms %K Artifacts %K Brain %K Brain Mapping %K Electroencephalography %K Evoked Potentials, Visual %K Feedback %K Humans %K Middle Aged %K Nervous System Diseases %K Research %K Research Design %K User-Computer Interface %K Visual Perception %X

Brain-computer interface (BCI) research at the Wadsworth Center has focused primarily on using electroencephalogram (EEG) rhythms recorded from the scalp over sensorimotor cortex to control cursor movement in one or two dimensions. Recent and current studies seek to improve the speed and accuracy of this control by improving the selection of signal features and their translation into device commands, by incorporating additional signal features, and by optimizing the adaptive interaction between the user and system. In addition, to facilitate the evaluation, comparison, and combination of alternative BCI methods, we have developed a general-purpose BCI system called BCI-2000 and have made it available to other research groups. Finally, in collaboration with several other groups, we are developing simple BCI applications and are testing their practicality and long-term value for people with severe motor disabilities.

%B IEEE Trans Neural Syst Rehabil Eng %V 11 %P 204-7 %8 06/2003 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/12899275 %N 2 %R 10.1109/TNSRE.2003.814442