TY - JOUR T1 - Modulation in cortical excitability disrupts information transfer in perceptual-level stimulus processing. JF - Neuroimage Y1 - 2021 A1 - Moheimanian, Ladan A1 - Paraskevopoulou, Sivylla E A1 - Adamek, Markus A1 - Schalk, Gerwin A1 - Peter Brunner KW - Acoustic Stimulation KW - Adult KW - Aged KW - Alpha Rhythm KW - Auditory Cortex KW - Brain Mapping KW - Cortical Excitability KW - Electrocorticography KW - Female KW - Humans KW - Male KW - Middle Aged AB -

Despite significant interest in the neural underpinnings of behavioral variability, little light has been shed on the cortical mechanism underlying the failure to respond to perceptual-level stimuli. We hypothesized that cortical activity resulting from perceptual-level stimuli is sensitive to the moment-to-moment fluctuations in cortical excitability, and thus may not suffice to produce a behavioral response. We tested this hypothesis using electrocorticographic recordings to follow the propagation of cortical activity in six human subjects that responded to perceptual-level auditory stimuli. Here we show that for presentations that did not result in a behavioral response, the likelihood of cortical activity decreased from auditory cortex to motor cortex, and was related to reduced local cortical excitability. Cortical excitability was quantified using instantaneous voltage during a short window prior to cortical activity onset. Therefore, when humans are presented with an auditory stimulus close to perceptual-level threshold, moment-by-moment fluctuations in cortical excitability determine whether cortical responses to sensory stimulation successfully connect auditory input to a resultant behavioral response.

VL - 243 ER - TY - JOUR T1 - Within-subject reaction time variability: Role of cortical networks and underlying neurophysiological mechanisms. JF - Neuroimage Y1 - 2021 A1 - Paraskevopoulou, Sivylla E A1 - Coon, William G A1 - Peter Brunner A1 - Miller, Kai J A1 - Schalk, Gerwin KW - Adult KW - Algorithms KW - Alpha Rhythm KW - Cerebral Cortex KW - Connectome KW - Electrocorticography KW - Female KW - Gamma Rhythm KW - Humans KW - Male KW - Middle Aged KW - Nerve Net KW - Psychomotor Performance KW - Reaction Time KW - Young Adult AB -

Variations in reaction time are a ubiquitous characteristic of human behavior. Extensively documented, they have been successfully modeled using parameters of the subject or the task, but the neural basis of behavioral reaction time that varies within the same subject and the same task has been minimally studied. In this paper, we investigate behavioral reaction time variance using 28 datasets of direct cortical recordings in humans who engaged in four different types of simple sensory-motor reaction time tasks. Using a previously described technique that can identify the onset of population-level cortical activity and a novel functional connectivity algorithm described herein, we show that the cumulative latency difference of population-level neural activity across the task-related cortical network can explain up to 41% of the trial-by-trial variance in reaction time. Furthermore, we show that reaction time variance may primarily be due to the latencies in specific brain regions and demonstrate that behavioral latency variance is accumulated across the whole task-related cortical network. Our results suggest that population-level neural activity monotonically increases prior to movement execution, and that trial-by-trial changes in that increase are, in part, accounted for by inhibitory activity indexed by low-frequency oscillations. This pre-movement neural activity explains 19% of the measured variance in neural latencies in our data. Thus, our study provides a mechanistic explanation for a sizable fraction of behavioral reaction time when the subject's task is the same from trial to trial.

VL - 237 ER - TY - JOUR T1 - Potential differences between monolingual and bilingual patients in approach and outcome after awake brain surgery. JF - J Neurooncol Y1 - 2020 A1 - ReFaey, Karim A1 - Tripathi, Shashwat A1 - Bhargav, Adip G A1 - Grewal, Sanjeet S A1 - Middlebrooks, Erik H A1 - Sabsevitz, David S A1 - Jentoft, Mark A1 - Peter Brunner A1 - Wu, Adela A1 - Tatum, William O A1 - Ritaccio, Anthony A1 - Chaichana, Kaisorn L A1 - Quinones-Hinojosa, Alfredo KW - Brain Mapping KW - Brain Neoplasms KW - Craniotomy KW - Female KW - Follow-Up Studies KW - Glioma KW - Humans KW - Incidence KW - Language KW - Male KW - Middle Aged KW - Monitoring, Intraoperative KW - Prognosis KW - Retrospective Studies KW - Seizures KW - United States KW - Wakefulness AB -

INTRODUCTION: 20.8% of the United States population and 67% of the European population speak two or more languages. Intraoperative different languages, mapping, and localization are crucial. This investigation aims to address three questions between BL and ML patients: (1) Are there differences in complications (i.e. seizures) and DECS techniques during intra-operative brain mapping? (2) Is EOR different? and (3) Are there differences in the recovery pattern post-surgery?

METHODS: Data from 56 patients that underwent left-sided awake craniotomy for tumors infiltrating possible dominant hemisphere language areas from September 2016 to June 2019 were identified and analyzed in this study; 14 BL and 42 ML control patients. Patient demographics, education level, and the age of language acquisition were documented and evaluated. fMRI was performed on all participants.

RESULTS: 0 (0%) BL and 3 (7%) ML experienced intraoperative seizures (P = 0.73). BL patients received a higher direct DECS current in comparison to the ML patients (average = 4.7, 3.8, respectively, P = 0.03). The extent of resection was higher in ML patients in comparison to the BL patients (80.9 vs. 64.8, respectively, P = 0.04). The post-operative KPS scores were higher in BL patients in comparison to ML patients (84.3, 77.4, respectively, P = 0.03). BL showed lower drop in post-operative KPS in comparison to ML patients (- 4.3, - 8.7, respectively, P = 0.03).

CONCLUSION: We show that BL patients have a lower incidence of intra-operative seizures, lower EOR, higher post-operative KPS and tolerate higher DECS current, in comparison to ML patients.

VL - 148 IS - 3 ER - TY - JOUR T1 - Brain-computer interface (BCI) evaluation in people with amyotrophic lateral sclerosis. JF - Amyotroph Lateral Scler Frontotemporal Degener Y1 - 2014 A1 - McCane, Lynn M A1 - Sellers, Eric W A1 - Dennis J. McFarland A1 - Mak, Joseph N A1 - Carmack, C Steve A1 - Zeitlin, Debra A1 - Jonathan Wolpaw A1 - Theresa M Vaughan KW - Adult KW - Aged KW - Amyotrophic Lateral Sclerosis KW - Biofeedback, Psychology KW - brain-computer interfaces KW - Communication Disorders KW - Electroencephalography KW - Event-Related Potentials, P300 KW - Female KW - Humans KW - Male KW - Middle Aged KW - Online Systems KW - Photic Stimulation KW - Psychomotor Performance KW - Reaction Time AB - Brain-computer interfaces (BCIs) might restore communication to people severely disabled by amyotrophic lateral sclerosis (ALS) or other disorders. We sought to: 1) define a protocol for determining whether a person with ALS can use a visual P300-based BCI; 2) determine what proportion of this population can use the BCI; and 3) identify factors affecting BCI performance. Twenty-five individuals with ALS completed an evaluation protocol using a standard 6 × 6 matrix and parameters selected by stepwise linear discrimination. With an 8-channel EEG montage, the subjects fell into two groups in BCI accuracy (chance accuracy 3%). Seventeen averaged 92 (± 3)% (range 71-100%), which is adequate for communication (G70 group). Eight averaged 12 (± 6)% (range 0-36%), inadequate for communication (L40 subject group). Performance did not correlate with disability: 11/17 (65%) of G70 subjects were severely disabled (i.e. ALSFRS-R < 5). All L40 subjects had visual impairments (e.g. nystagmus, diplopia, ptosis). P300 was larger and more anterior in G70 subjects. A 16-channel montage did not significantly improve accuracy. In conclusion, most people severely disabled by ALS could use a visual P300-based BCI for communication. In those who could not, visual impairment was the principal obstacle. For these individuals, auditory P300-based BCIs might be effective. VL - 15 UR - http://www.ncbi.nlm.nih.gov/pubmed/24555843 IS - 3-4 ER - TY - JOUR T1 - Locomotor impact of beneficial or nonbeneficial H-reflex conditioning after spinal cord injury. JF - J Neurophysiol Y1 - 2014 A1 - Yi Chen A1 - Lu Chen A1 - Liu, Rongliang A1 - Wang, Yu A1 - Xiang Yang Chen A1 - Jonathan Wolpaw KW - Animals KW - Conditioning, Operant KW - Female KW - H-Reflex KW - Learning KW - Locomotion KW - Male KW - Rats KW - Rats, Sprague-Dawley KW - Spinal Cord Injuries AB - When new motor learning changes neurons and synapses in the spinal cord, it may affect previously learned behaviors that depend on the same spinal neurons and synapses. To explore these effects, we used operant conditioning to strengthen or weaken the right soleus H-reflex pathway in rats in which a right spinal cord contusion had impaired locomotion. When up-conditioning increased the H-reflex, locomotion improved. Steps became longer, and step-cycle asymmetry (i.e., limping) disappeared. In contrast, when down-conditioning decreased the H-reflex, locomotion did not worsen. Steps did not become shorter, and asymmetry did not increase. Electromyographic and kinematic analyses explained how H-reflex increase improved locomotion and why H-reflex decrease did not further impair it. Although the impact of up-conditioning or down-conditioning on the H-reflex pathway was still present during locomotion, only up-conditioning affected the soleus locomotor burst. Additionally, compensatory plasticity apparently prevented the weaker H-reflex pathway caused by down-conditioning from weakening the locomotor burst and further impairing locomotion. The results support the hypothesis that the state of the spinal cord is a "negotiated equilibrium" that serves all the behaviors that depend on it. When new learning changes the spinal cord, old behaviors undergo concurrent relearning that preserves or improves their key features. Thus, if an old behavior has been impaired by trauma or disease, spinal reflex conditioning, by changing a specific pathway and triggering a new negotiation, may enable recovery beyond that achieved simply by practicing the old behavior. Spinal reflex conditioning protocols might complement other neurorehabilitation methods and enhance recovery. VL - 111 UR - http://www.ncbi.nlm.nih.gov/pubmed/24371288 IS - 6 ER - TY - JOUR T1 - A practical, intuitive brain-computer interface for communicating 'yes' or 'no' by listening. JF - J Neural Eng Y1 - 2014 A1 - Jeremy Jeremy Hill A1 - Ricci, Erin A1 - Haider, Sameah A1 - McCane, Lynn M A1 - Susan M Heckman A1 - Jonathan Wolpaw A1 - Theresa M Vaughan KW - Adult KW - Aged KW - Algorithms KW - Auditory Perception KW - brain-computer interfaces KW - Communication Aids for Disabled KW - Electroencephalography KW - Equipment Design KW - Equipment Failure Analysis KW - Female KW - Humans KW - Male KW - Man-Machine Systems KW - Middle Aged KW - Quadriplegia KW - Treatment Outcome KW - User-Computer Interface AB - OBJECTIVE: Previous work has shown that it is possible to build an EEG-based binary brain-computer interface system (BCI) driven purely by shifts of attention to auditory stimuli. However, previous studies used abrupt, abstract stimuli that are often perceived as harsh and unpleasant, and whose lack of inherent meaning may make the interface unintuitive and difficult for beginners. We aimed to establish whether we could transition to a system based on more natural, intuitive stimuli (spoken words 'yes' and 'no') without loss of performance, and whether the system could be used by people in the locked-in state. APPROACH: We performed a counterbalanced, interleaved within-subject comparison between an auditory streaming BCI that used beep stimuli, and one that used word stimuli. Fourteen healthy volunteers performed two sessions each, on separate days. We also collected preliminary data from two subjects with advanced amyotrophic lateral sclerosis (ALS), who used the word-based system to answer a set of simple yes-no questions. MAIN RESULTS: The N1, N2 and P3 event-related potentials elicited by words varied more between subjects than those elicited by beeps. However, the difference between responses to attended and unattended stimuli was more consistent with words than beeps. Healthy subjects' performance with word stimuli (mean 77% ± 3.3 s.e.) was slightly but not significantly better than their performance with beep stimuli (mean 73% ± 2.8 s.e.). The two subjects with ALS used the word-based BCI to answer questions with a level of accuracy similar to that of the healthy subjects. SIGNIFICANCE: Since performance using word stimuli was at least as good as performance using beeps, we recommend that auditory streaming BCI systems be built with word stimuli to make the system more pleasant and intuitive. Our preliminary data show that word-based streaming BCI is a promising tool for communication by people who are locked in. VL - 11 UR - http://www.ncbi.nlm.nih.gov/pubmed/24838278 IS - 3 ER - TY - JOUR T1 - Novel inter-hemispheric white matter connectivity in the BTBR mouse model of autism. JF - Brain Res Y1 - 2013 A1 - Miller, V M A1 - Disha Gupta A1 - Neu, N A1 - Cotroneo, A A1 - Chadwick B. Boulay A1 - Seegal, R F KW - Analysis of Variance KW - Animals KW - Autistic Disorder KW - Brain KW - Corpus Callosum KW - Disease Models, Animal KW - Electroencephalography KW - Enzyme-Linked Immunosorbent Assay KW - Female KW - Functional Laterality KW - Image Processing, Computer-Assisted KW - Male KW - Mice KW - Mice, Inbred C57BL KW - Mice, Neurologic Mutants KW - Microtubule-Associated Proteins KW - Myelin Basic Protein KW - Nerve Fibers, Myelinated KW - Neuroimaging KW - Spectrum Analysis AB - Alterations in the volume, density, connectivity and functional activation of white matter tracts are reported in some individuals with autism and may contribute to their abnormal behaviors. The BTBR (BTBR T+tf/J) inbred strain of mouse, is used to model facets of autism because they develop low social behaviors, stereotypical and immune changes similar to those found in people with autism. Previously, it was thought a total absence of corpus callosal interhemispheric connective tissues in the BTBR mice may underlie their abnormal behaviors. However, postnatal lesions of the corpus callosum do not precipitate social behavioral problems in other strains of mice suggesting a flaw in this theory. In this study we used digital pathological methods to compare subcortical white matter connective tracts in the BTBR strain of mice with those found in the C57Bl/6 mouse and those reported in a standardized mouse brain atlas. We report, for the first time, a novel connective subcortical interhemispheric bridge of tissue in the posterior, but not anterior, cerebrum of the BTBR mouse. These novel connective tissues are comprised of myelinated fibers, with reduced myelin basic protein levels (MBP) compared to levels in the C57Bl/6 mouse. We used electrophysiological analysis and found increased inter-hemispheric connectivity in the posterior hemispheres of the BTBR strain compared with the anterior hemispheres. The conduction velocity was slower than that reported in normal mice. This study shows there is novel abnormal interhemispheric connectivity in the BTBR strain of mice, which may contribute to their behavioral abnormalities. VL - 1513 UR - http://www.ncbi.nlm.nih.gov/pubmed/23570707 ER - TY - JOUR T1 - Questionable reliability of the speech-evoked auditory brainstem response (sABR) in typically-developing children. JF - Hear Res Y1 - 2012 A1 - Dennis J. McFarland A1 - Cacace, Anthony T KW - Evoked Potentials, Auditory, Brain Stem KW - Female KW - Hearing Tests KW - Humans KW - Male KW - Speech Perception VL - 287 UR - http://www.ncbi.nlm.nih.gov/pubmed/22446178 IS - 1-2 ER - TY - JOUR T1 - Causal influence of gamma oscillations on the sensorimotor rhythm. JF - Neuroimage Y1 - 2011 A1 - Grosse-Wentrup, Moritz A1 - Schölkopf, B A1 - Jeremy Jeremy Hill KW - Adult KW - Cerebral Cortex KW - Electroencephalography KW - Female KW - Humans KW - Imagination KW - Male KW - Signal Processing, Computer-Assisted KW - User-Computer Interface AB -

Gamma oscillations of the electromagnetic field of the brain are known to be involved in a variety of cognitive processes, and are believed to be fundamental for information processing within the brain. While gamma oscillations have been shown to be correlated with brain rhythms at different frequencies, to date no empirical evidence has been presented that supports a causal influence of gamma oscillations on other brain rhythms. In this work, we study the relation of gamma oscillations and the sensorimotor rhythm (SMR) in healthy human subjects using electroencephalography. We first demonstrate that modulation of the SMR, induced by motor imagery of either the left or right hand, is positively correlated with the power of frontal and occipital gamma oscillations, and negatively correlated with the power of centro-parietal gamma oscillations. We then demonstrate that the most simple causal structure, capable of explaining the observed correlation of gamma oscillations and the SMR, entails a causal influence of gamma oscillations on the SMR. This finding supports the fundamental role attributed to gamma oscillations for information processing within the brain, and is of particular importance for brain-computer interfaces (BCIs). As modulation of the SMR is typically used in BCIs to infer a subject's intention, our findings entail that gamma oscillations have a causal influence on a subject's capability to utilize a BCI for means of communication.

VL - 56 UR - http://www.ncbi.nlm.nih.gov/pubmed/20451626 IS - 2 ER - TY - JOUR T1 - Closing the sensorimotor loop: haptic feedback facilitates decoding of motor imagery. JF - J Neural Eng Y1 - 2011 A1 - Gomez-Rodriguez, M A1 - Peters, J A1 - Jeremy Jeremy Hill A1 - Schölkopf, B A1 - Gharabaghi, A A1 - Grosse-Wentrup, Moritz KW - Brain KW - Evoked Potentials, Motor KW - Evoked Potentials, Somatosensory KW - Feedback, Physiological KW - Female KW - Humans KW - Imagination KW - Male KW - Movement KW - Robotics KW - Touch KW - User-Computer Interface AB -

The combination of brain-computer interfaces (BCIs) with robot-assisted physical therapy constitutes a promising approach to neurorehabilitation of patients with severe hemiparetic syndromes caused by cerebrovascular brain damage (e.g. stroke) and other neurological conditions. In such a scenario, a key aspect is how to reestablish the disrupted sensorimotor feedback loop. However, to date it is an open question how artificially closing the sensorimotor feedback loop influences the decoding performance of a BCI. In this paper, we answer this issue by studying six healthy subjects and two stroke patients. We present empirical evidence that haptic feedback, provided by a seven degrees of freedom robotic arm, facilitates online decoding of arm movement intention. The results support the feasibility of future rehabilitative treatments based on the combination of robot-assisted physical therapy with BCIs.

VL - 8 UR - http://www.ncbi.nlm.nih.gov/pubmed/21474878 IS - 3 ER - TY - JOUR T1 - Decoding vowels and consonants in spoken and imagined words using electrocorticographic signals in humans. JF - J Neural Eng Y1 - 2011 A1 - Pei, Xiao-Mei A1 - Barbour, Dennis L A1 - Leuthardt, E C A1 - Gerwin Schalk KW - Adolescent KW - Adult KW - Brain KW - Brain Mapping KW - Cerebral Cortex KW - Communication Aids for Disabled KW - Data Interpretation, Statistical KW - Discrimination (Psychology) KW - Electrodes, Implanted KW - Electroencephalography KW - Epilepsy KW - Female KW - Functional Laterality KW - Humans KW - Male KW - Middle Aged KW - Movement KW - Speech Perception KW - User-Computer Interface AB -

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.

VL - 8 UR - http://www.ncbi.nlm.nih.gov/pubmed/21750369 IS - 4 ER - TY - JOUR T1 - Dichotic and dichoptic digit perception in normal adults. JF - J Am Acad Audiol Y1 - 2011 A1 - Lawfield, Angela A1 - Dennis J. McFarland A1 - Cacace, Anthony T KW - Adolescent KW - Adult KW - Auditory Perception KW - Dichotic Listening Tests KW - Female KW - Functional Laterality KW - Humans KW - Male KW - Recognition (Psychology) KW - Reference Values KW - Reproducibility of Results KW - Task Performance and Analysis KW - Visual Perception KW - Young Adult AB - BACKGROUND: Verbally based dichotic-listening experiments and reproduction-mediated response-selection strategies have been used for over four decades to study perceptual/cognitive aspects of auditory information processing and make inferences about hemispheric asymmetries and language lateralization in the brain. Test procedures using dichotic digits have also been used to assess for disorders of auditory processing. However, with this application, limitations exist and paradigms need to be developed to improve specificity of the diagnosis. Use of matched tasks in multiple sensory modalities is a logical approach to address this issue. Herein, we use dichotic listening and dichoptic viewing of visually presented digits for making this comparison. PURPOSE: To evaluate methodological issues involved in using matched tasks of dichotic listening and dichoptic viewing in normal adults. RESEARCH DESIGN: A multivariate assessment of the effects of modality (auditory vs. visual), digit-span length (1-3 pairs), response selection (recognition vs. reproduction), and ear/visual hemifield of presentation (left vs. right) on dichotic and dichoptic digit perception. STUDY SAMPLE: Thirty adults (12 males, 18 females) ranging in age from 18 to 30 yr with normal hearing sensitivity and normal or corrected-to-normal visual acuity. DATA COLLECTION AND ANALYSIS: A computerized, custom-designed program was used for all data collection and analysis. A four-way repeated measures analysis of variance (ANOVA) evaluated the effects of modality, digit-span length, response selection, and ear/visual field of presentation. RESULTS: The ANOVA revealed that performances on dichotic listening and dichoptic viewing tasks were dependent on complex interactions between modality, digit-span length, response selection, and ear/visual hemifield of presentation. Correlation analysis suggested a common effect on overall accuracy of performance but isolated only an auditory factor for a laterality index. CONCLUSIONS: The variables used in this experiment affected performances in the auditory modality to a greater extent than in the visual modality. The right-ear advantage observed in the dichotic-digits task was most evident when reproduction mediated response selection was used in conjunction with three-digit pairs. This effect implies that factors such as "speech related output mechanisms" and digit-span length (working memory) contribute to laterality effects in dichotic listening performance with traditional paradigms. Thus, the use of multiple-digit pairs to avoid ceiling effects and the application of verbal reproduction as a means of response selection may accentuate the role of nonperceptual factors in performance. Ideally, tests of perceptual abilities should be relatively free of such effects. VL - 22 UR - http://www.ncbi.nlm.nih.gov/pubmed/21864471 IS - 6 ER - TY - JOUR T1 - Nonuniform high-gamma (60-500 Hz) power changes dissociate cognitive task and anatomy in human cortex. JF - J Neurosci Y1 - 2011 A1 - Charles M Gaona A1 - Sharma, Mohit A1 - Zachary V. Freudenberg A1 - Breshears, Jonathan A1 - Bundy, David T A1 - Roland, Jarod A1 - Barbour, Dennis L A1 - Gerwin Schalk A1 - Leuthardt, E C KW - Acoustic Stimulation KW - Adolescent KW - Adult KW - Analysis of Variance KW - Brain Mapping KW - Brain Waves KW - Cerebral Cortex KW - Cognition Disorders KW - Electroencephalography KW - Epilepsy KW - Evoked Potentials KW - Female KW - Humans KW - Male KW - Middle Aged KW - Neuropsychological Tests KW - Nonlinear Dynamics KW - Photic Stimulation KW - Reaction Time KW - Spectrum Analysis KW - Time Factors KW - Vocabulary AB -

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.

VL - 31 UR - http://www.ncbi.nlm.nih.gov/pubmed/21307246 IS - 6 ER - TY - JOUR T1 - Spatiotemporal dynamics of electrocorticographic high gamma activity during overt and covert word repetition. JF - Neuroimage Y1 - 2011 A1 - Pei, Xiao-Mei A1 - Leuthardt, E C A1 - Charles M Gaona A1 - Peter Brunner A1 - Jonathan Wolpaw A1 - Gerwin Schalk KW - Adolescent KW - Adult KW - Brain KW - Brain Mapping KW - Electroencephalography KW - Female KW - Humans KW - Male KW - Middle Aged KW - Signal Processing, Computer-Assisted KW - Verbal Behavior AB -

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.

VL - 54 UR - http://www.ncbi.nlm.nih.gov/pubmed/21029784 IS - 4 ER - TY - JOUR T1 - Transition from the locked in to the completely locked-in state: a physiological analysis. JF - Clin Neurophysiol Y1 - 2011 A1 - Murguialday, A Ramos A1 - Jeremy Jeremy Hill A1 - Bensch, M A1 - Martens, S M M A1 - S Halder A1 - Nijboer, F A1 - Schoelkopf, Bernhard A1 - Niels Birbaumer A1 - Gharabaghi, A KW - Adult KW - Amyotrophic Lateral Sclerosis KW - Area Under Curve KW - Brain KW - Communication Aids for Disabled KW - Disease Progression KW - Electroencephalography KW - Electromyography KW - Humans KW - Male KW - Signal Processing, Computer-Assisted KW - User-Computer Interface AB -

OBJECTIVE: 

To clarify the physiological and behavioral boundaries between locked-in (LIS) and the completely locked-in state (CLIS) (no voluntary eye movements, no communication possible) through electrophysiological data and to secure brain-computer-interface (BCI) communication.

METHODS: 

Electromyography from facial muscles, external anal sphincter (EAS), electrooculography and electrocorticographic data during different psychophysiological tests were acquired to define electrophysiological differences in an amyotrophic lateral sclerosis (ALS) patient with an intracranially implanted grid of 112 electrodes for nine months while the patient passed from the LIS to the CLIS.

RESULTS: 

At the very end of the LIS there was no facial muscle activity, nor external anal sphincter but eye control. Eye movements were slow and lasted for short periods only. During CLIS event related brainpotentials (ERP) to passive limb movements and auditory stimuli were recorded, vibrotactile stimulation of different body parts resulted in no ERP response.

CONCLUSIONS: 

The results presented contradict the commonly accepted assumption that the EAS is the last remaining muscle under voluntary control and demonstrate complete loss of eye movements in CLIS. The eye muscle was shown to be the last muscle group under voluntary control. The findings suggest ALS as a multisystem disorder, even affecting afferent sensory pathways.

SIGNIFICANCE: 

Auditory and proprioceptive brain-computer-interface (BCI) systems are the only remaining communication channels in CLIS.

VL - 122 UR - http://www.ncbi.nlm.nih.gov/pubmed/20888292 IS - 5 ER - TY - JOUR T1 - Using the electrocorticographic speech network to control a brain-computer interface in humans. JF - J Neural Eng Y1 - 2011 A1 - Leuthardt, E C A1 - Charles M Gaona A1 - Sharma, Mohit A1 - Szrama, Nicholas A1 - Roland, Jarod A1 - Zachary V. Freudenberg A1 - Solisb, Jamie A1 - Breshears, Jonathan A1 - Gerwin Schalk KW - Adult KW - Brain KW - Brain Mapping KW - Computer Peripherals KW - Electroencephalography KW - Evoked Potentials KW - Feedback, Physiological KW - Female KW - Humans KW - Imagination KW - Male KW - Middle Aged KW - Nerve Net KW - Speech Production Measurement KW - User-Computer Interface AB -

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.

VL - 8 UR - http://www.ncbi.nlm.nih.gov/pubmed/21471638 IS - 3 ER - TY - JOUR T1 - Cortical activity during motor execution, motor imagery, and imagery-based online feedback. JF - Proc Natl Acad Sci U S A Y1 - 2010 A1 - Miller, K.J. A1 - Gerwin Schalk A1 - Fetz, Eberhard E A1 - den Nijs, Marcel A1 - Ojemann, J G A1 - Rao, Rajesh P N KW - Adolescent KW - Adult KW - Biofeedback, Psychology KW - Cerebral Cortex KW - Child KW - Electric Stimulation KW - Electrocardiography KW - Female KW - Humans KW - Male KW - Middle Aged KW - Motor Activity KW - Young Adult AB -

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.

VL - 107 UR - http://www.ncbi.nlm.nih.gov/pubmed/20160084 IS - 9 ER - TY - JOUR T1 - Does the 'P300' speller depend on eye gaze?. JF - J Neural Eng Y1 - 2010 A1 - Peter Brunner A1 - Joshi, S A1 - S Briskin A1 - Jonathan Wolpaw A1 - H Bischof A1 - Gerwin Schalk KW - Adult KW - Event-Related Potentials, P300 KW - Eye Movements KW - Female KW - Humans KW - Male KW - Middle Aged KW - Models, Neurological KW - Photic Stimulation KW - User-Computer Interface KW - Young Adult AB -

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.

VL - 7 UR - http://www.ncbi.nlm.nih.gov/pubmed/20858924 IS - 5 ER - TY - JOUR T1 - Electrocorticographic frequency alteration mapping for extraoperative localization of speech cortex. JF - Neurosurgery Y1 - 2010 A1 - Wu, Melinda A1 - Wisneski, Kimberly A1 - Gerwin Schalk A1 - Sharma, Mohit A1 - Roland, Jarod A1 - Breshears, Jonathan A1 - Charles M Gaona A1 - Leuthardt, E C KW - Acoustic Stimulation KW - Adolescent KW - Adult KW - Brain Mapping KW - Cerebral Cortex KW - Chi-Square Distribution KW - Electroencephalography KW - Epilepsy KW - Female KW - Humans KW - Male KW - Mass Spectrometry KW - Middle Aged KW - Photic Stimulation KW - Speech KW - Verbal Behavior KW - Young Adult AB -

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.

VL - 66 UR - http://www.ncbi.nlm.nih.gov/pubmed/20087111 IS - 2 ER - TY - JOUR T1 - Decoding flexion of individual fingers using electrocorticographic signals in humans. JF - J Neural Eng Y1 - 2009 A1 - Kubánek, J A1 - Miller, John W A1 - Ojemann, J G A1 - Jonathan Wolpaw A1 - Gerwin Schalk KW - Adolescent KW - Adult KW - Biomechanics KW - Brain KW - Electrodiagnosis KW - Epilepsy KW - Female KW - Fingers KW - Humans KW - Male KW - Microelectrodes KW - Middle Aged KW - Motor Activity KW - Rest KW - Thumb KW - Time Factors KW - Young Adult AB -

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.

VL - 6 UR - http://www.ncbi.nlm.nih.gov/pubmed/19794237 IS - 6 ER - TY - Generic T1 - Detection of spontaneous class-specific visual stimuli with high temporal accuracy in human electrocorticography. T2 - Conf Proc IEEE Eng Med Biol Soc Y1 - 2009 A1 - Miller, John W A1 - Hermes, Dora A1 - Gerwin Schalk A1 - Ramsey, Nick F A1 - Jagadeesh, Bharathi A1 - den Nijs, Marcel A1 - Ojemann, J G A1 - Rao, Rajesh P N KW - Algorithms KW - Electrocardiography KW - Evoked Potentials, Visual KW - Humans KW - Male KW - Pattern Recognition, Automated KW - Pattern Recognition, Visual KW - Photic Stimulation KW - Reproducibility of Results KW - Sensitivity and Specificity KW - User-Computer Interface KW - Visual Cortex AB - Most brain-computer interface classification experiments from electrical potential recordings have been focused on the identification of classes of stimuli or behavior where the timing of experimental parameters is known or pre-designated. Real world experience, however, is spontaneous, and to this end we describe an experiment predicting the occurrence, timing, and types of visual stimuli perceived by a human subject from electrocorticographic recordings. All 300 of 300 presented stimuli were correctly detected, with a temporal precision of order 20 ms. The type of stimulus (face/house) was correctly identified in 95% of these cases. There were approximately 20 false alarm events, corresponding to a late 2nd neuronal response to a previously identified event. JF - Conf Proc IEEE Eng Med Biol Soc VL - 2009 ER - TY - JOUR T1 - Power spectrum analysis on the multiparameter electroencephalogram features of physiological mental fatigue. JF - Sheng Wu Yi Xue Gong Cheng Xue Za Zhi Y1 - 2009 A1 - Zhang, Ai-hua A1 - Zheng, Shi Dong A1 - Pei, Xiao-Mei A1 - Ouyang, Yi KW - Adult KW - Electroencephalography KW - Entropy KW - Humans KW - Male KW - Mental Fatigue KW - Signal Processing, Computer-Assisted KW - Young Adult AB -

The aim of this experiment is to find a feasible impersonal index for analyzing the physiological mental fatigue level. Three characteristic parameters, relative power in different rhythm, barycenter frequency and power spectral entropy, are extracted from two channels' electroencephalogram (EEG) under two physiological mental fatigue states. Then relationships between such three parameters and physiological mental fatigue are analyzed to explore whether they can be of use for detecting (or monitoring) the mental fatigue level. The experiment results show that the relative power, barycenter frequency and power spectral entropy of EEG exhibit strong correlation with physiological mental fatigue level. While physiological mental fatigue level increases, the relative power in theta, alpha and beta rhythms, barycenter frequency and power spectral entropy of EEG decrease, but the relative power in delta rhythm of EEG increases. The relative power in four rhythms, barycenter frequency and power spectral entropy of EEG reflect the change of physiological mental fatigue level sensitively, and may hopefully be used as indexes for detecting physiological mental fatigue level.

VL - 26 UR - http://www.ncbi.nlm.nih.gov/pubmed/19334577 IS - 1 ER - TY - JOUR T1 - A practical procedure for real-time functional mapping of eloquent cortex using electrocorticographic signals in humans. JF - Epilepsy Behav Y1 - 2009 A1 - Peter Brunner A1 - A L Ritaccio A1 - Lynch, Timothy M A1 - Emrich, Joseph F A1 - Adam J Wilson A1 - Williams, Justin C A1 - Aarnoutse, Erik J A1 - Ramsey, Nick F A1 - Leuthardt, E C A1 - H Bischof A1 - Gerwin Schalk KW - Adult KW - Brain Mapping KW - Cerebral Cortex KW - Electric Stimulation KW - Electrodes, Implanted KW - Electroencephalography KW - Epilepsy KW - Female KW - Humans KW - Male KW - Middle Aged KW - Practice Guidelines as Topic KW - Signal Processing, Computer-Assisted KW - Young Adult AB -

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.

VL - 15 UR - http://www.ncbi.nlm.nih.gov/pubmed/19366638 IS - 3 ER - TY - JOUR T1 - Brain-computer interfaces (BCIs): Detection Instead of Classification. JF - J Neurosci Methods Y1 - 2008 A1 - Gerwin Schalk A1 - Peter Brunner A1 - Lester A Gerhardt A1 - H Bischof A1 - Jonathan Wolpaw KW - Adult KW - Algorithms KW - Brain KW - Brain Mapping KW - Electrocardiography KW - Electroencephalography KW - Humans KW - Male KW - Man-Machine Systems KW - Normal Distribution KW - Online Systems KW - Signal Detection, Psychological KW - Signal Processing, Computer-Assisted KW - Software Validation KW - User-Computer Interface AB -

Many studies over the past two decades have shown that people can use brain signals to convey their intent to a computer through brain-computer interfaces (BCIs). These devices operate by recording signals from the brain and translating these signals into device commands. They can be used by people who are severely paralyzed to communicate without any use of muscle activity. One of the major impediments in translating this novel technology into clinical applications is the current requirement for preliminary analyses to identify the brain signal features best suited for communication. This paper introduces and validates signal detection, which does not require such analysis procedures, as a new concept in BCI signal processing. This detection concept is realized with Gaussian mixture models (GMMs) that are used to model resting brain activity so that any change in relevant brain signals can be detected. It is implemented in a package called SIGFRIED (SIGnal modeling For Real-time Identification and Event Detection). The results indicate that SIGFRIED produces results that are within the range of those achieved using a common analysis strategy that requires preliminary identification of signal features. They indicate that such laborious analysis procedures could be replaced by merely recording brain signals during rest. In summary, this paper demonstrates how SIGFRIED could be used to overcome one of the present impediments to translation of laboratory BCI demonstrations into clinically practical applications.

VL - 167 UR - http://www.ncbi.nlm.nih.gov/pubmed/17920134 IS - 1 ER - TY - JOUR T1 - Non-invasive brain-computer interface system: towards its application as assistive technology. JF - Brain Res Bull Y1 - 2008 A1 - Cincotti, F A1 - Mattia, Donatella A1 - Aloise, Fabio A1 - Bufalari, Simona A1 - Gerwin Schalk A1 - Oriolo, Giuseppe A1 - Cherubini, Andrea A1 - Marciani, Maria Grazia A1 - Babiloni, Fabio KW - Activities of Daily Living KW - Adolescent KW - Adult KW - Brain KW - Child KW - Electroencephalography KW - Evoked Potentials, Motor KW - Female KW - Humans KW - Learning KW - Male KW - Middle Aged KW - Motor Skills KW - Muscular Dystrophy, Duchenne KW - Pilot Projects KW - Prostheses and Implants KW - Robotics KW - Self-Help Devices KW - Software KW - Spinal Muscular Atrophies of Childhood KW - User-Computer Interface KW - Volition AB -

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.

VL - 75 UR - http://www.ncbi.nlm.nih.gov/pubmed/18394526 IS - 6 ER - TY - JOUR T1 - Real-time detection of event-related brain activity. JF - Neuroimage Y1 - 2008 A1 - Gerwin Schalk A1 - Leuthardt, E C A1 - Peter Brunner A1 - Ojemann, J G A1 - Lester A Gerhardt A1 - Jonathan Wolpaw KW - Adult KW - Algorithms KW - Brain Mapping KW - Computer Systems KW - Diagnosis, Computer-Assisted KW - Electroencephalography KW - Epilepsy KW - Evoked Potentials KW - Female KW - Humans KW - Male KW - Pattern Recognition, Automated KW - Reproducibility of Results KW - Sensitivity and Specificity AB -

The complexity and inter-individual variation of brain signals impedes real-time detection of events in raw signals. To convert these complex signals into results that can be readily understood, current approaches usually apply statistical methods to data from known conditions after all data have been collected. The capability to provide meaningful visualization of complex brain signals without the requirement to initially collect data from all conditions would provide a new tool, essentially a new imaging technique, that would open up new avenues for the study of brain function. Here we show that a new analysis approach, called SIGFRIED, can overcome this serious limitation of current methods. SIGFRIED can visualize brain signal changes without requiring prior data collection from all conditions. This capacity is particularly well suited to applications in which comprehensive prior data collection is impossible or impractical, such as intraoperative localization of cortical function or detection of epileptic seizures.

VL - 43 UR - http://www.ncbi.nlm.nih.gov/pubmed/18718544 IS - 2 ER - TY - Generic T1 - Three cases of feature correlation in an electrocorticographic BCI. T2 - Conf Proc IEEE Eng Med Biol Soc Y1 - 2008 A1 - Miller, John W A1 - Blakely, Timothy A1 - Gerwin Schalk A1 - den Nijs, Marcel A1 - Rao, Rajesh P N A1 - Ojemann, J G KW - Adolescent KW - Adult KW - Algorithms KW - Electrocardiography KW - Evoked Potentials, Motor KW - Female KW - Humans KW - Male KW - Middle Aged KW - Motor Cortex KW - Pattern Recognition, Automated KW - Statistics as Topic KW - Task Performance and Analysis KW - User-Computer Interface AB - 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. JF - Conf Proc IEEE Eng Med Biol Soc ER - TY - CONF T1 - Three cases of feature correlation in an electrocorticographic BCI. T2 - Engineering in Medicine and Biology Society, 2008. Y1 - 2008 A1 - Miller, Kai J A1 - Blakely, Timothy A1 - Gerwin Schalk A1 - den Nijs, Marcel A1 - Rao, Rajesh PN A1 - Ojemann, Jeffrey G KW - Adolescent KW - Adult KW - Algorithms KW - automated pattern recognition KW - control systems KW - decorrelation KW - Electrocardiography KW - Electrodes KW - Electroencephalography KW - evoked motor potentials KW - Feedback KW - Female KW - frequency KW - hospitals KW - Humans KW - Male KW - Middle Aged KW - Motor Cortex KW - Signal Processing KW - Statistics as Topic KW - Task Performance and Analysis KW - Tongue KW - User-Computer Interface AB - 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. JF - Engineering in Medicine and Biology Society, 2008. PB - IEEE CY - Vancouver, BC UR - http://www.ncbi.nlm.nih.gov/pubmed/19163918 ER - TY - JOUR T1 - Towards an independent brain-computer interface using steady state visual evoked potentials. JF - Clin Neurophysiol Y1 - 2008 A1 - Brendan Z. Allison A1 - Dennis J. McFarland A1 - Gerwin Schalk A1 - Zheng, Shi Dong A1 - Moore-Jackson, Melody A1 - Jonathan Wolpaw KW - Adolescent KW - Adult KW - Attention KW - Brain KW - Brain Mapping KW - Dose-Response Relationship, Radiation KW - Electroencephalography KW - Evoked Potentials, Visual KW - Female KW - Humans KW - Male KW - Pattern Recognition, Visual KW - Photic Stimulation KW - Spectrum Analysis KW - User-Computer Interface AB -

OBJECTIVE: 

Brain-computer interface (BCI) systems using steady state visual evoked potentials (SSVEPs) have allowed healthy subjects to communicate. However, these systems may not work in severely disabled users because they may depend on gaze shifting. This study evaluates the hypothesis that overlapping stimuli can evoke changes in SSVEP activity sufficient to control a BCI. This would provide evidence that SSVEP BCIs could be used without shifting gaze.

METHODS: 

Subjects viewed a display containing two images that each oscillated at a different frequency. Different conditions used overlapping or non-overlapping images to explore dependence on gaze function. Subjects were asked to direct attention to one or the other of these images during each of 12 one-minute runs.

RESULTS: 

Half of the subjects produced differences in SSVEP activity elicited by overlapping stimuli that could support BCI control. In all remaining users, differences did exist at corresponding frequencies but were not strong enough to allow effective control.

CONCLUSIONS: 

The data demonstrate that SSVEP differences sufficient for BCI control may be elicited by selective attention to one of two overlapping stimuli. Thus, some SSVEP-based BCI approaches may not depend on gaze control. The nature and extent of any BCI's dependence on muscle activity is a function of many factors, including the display, task, environment, and user.

SIGNIFICANCE: 

SSVEP BCIs might function in severely disabled users unable to reliably control gaze. Further research with these users is necessary to explore the optimal parameters of such a system and validate online performance in a home environment.

VL - 119 UR - http://www.ncbi.nlm.nih.gov/pubmed/18077208 IS - 2 ER - TY - JOUR T1 - Two-dimensional movement control using electrocorticographic signals in humans. JF - J Neural Eng Y1 - 2008 A1 - Gerwin Schalk A1 - Miller, K.J. A1 - Nicholas R Anderson A1 - Adam J Wilson A1 - Smyth, Matt A1 - Ojemann, J G A1 - Moran, D A1 - Jonathan Wolpaw A1 - Leuthardt, E C KW - Adolescent KW - Adult KW - Brain Mapping KW - Data Interpretation, Statistical KW - Drug Resistance KW - Electrocardiography KW - Electrodes, Implanted KW - Electroencephalography KW - Epilepsy KW - Female KW - Humans KW - Male KW - Movement KW - User-Computer Interface AB -

We show here that a brain-computer interface (BCI) using electrocorticographic activity (ECoG) and imagined or overt motor tasks enables humans to control a computer cursor in two dimensions. Over a brief training period of 12-36 min, each of five human subjects acquired substantial control of particular ECoG features recorded from several locations over the same hemisphere, and achieved average success rates of 53-73% in a two-dimensional four-target center-out task in which chance accuracy was 25%. Our results support the expectation that ECoG-based BCIs can combine high performance with technical and clinical practicality, and also indicate promising directions for further research.

VL - 5 UR - http://www.ncbi.nlm.nih.gov/pubmed/18310813 IS - 1 ER - TY - JOUR T1 - Unique cortical physiology associated with ipsilateral hand movements and neuroprosthetic implications. JF - Stroke Y1 - 2008 A1 - Wisneski, Kimberly A1 - Nicholas R Anderson A1 - Gerwin Schalk A1 - Smyth, Matt A1 - Moran, D A1 - Leuthardt, E C KW - Adolescent KW - Adult KW - Artificial Limbs KW - Bionics KW - Brain Mapping KW - Child KW - Dominance, Cerebral KW - Electroencephalography KW - Female KW - Hand KW - Humans KW - Male KW - Middle Aged KW - Motor Cortex KW - Movement KW - Paresis KW - Prosthesis Design KW - Psychomotor Performance KW - Stroke KW - User-Computer Interface KW - Volition AB -

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.

VL - 39 UR - http://www.ncbi.nlm.nih.gov/pubmed/18927456 IS - 12 ER - TY - JOUR T1 - Voluntary brain regulation and communication with electrocorticogram signals. JF - Epilepsy Behav Y1 - 2008 A1 - Hinterberger, T. A1 - Widman, Guido A1 - Lal, T.N A1 - Jeremy Jeremy Hill A1 - Tangermann, Michael A1 - Rosenstiel, W. A1 - Schölkopf, B A1 - Elger, Christian A1 - Niels Birbaumer KW - Adult KW - Biofeedback, Psychology KW - Cerebral Cortex KW - Communication Aids for Disabled KW - Dominance, Cerebral KW - Electroencephalography KW - Epilepsies, Partial KW - Female KW - Humans KW - Imagination KW - Male KW - Middle Aged KW - Motor Activity KW - Motor Cortex KW - Signal Processing, Computer-Assisted KW - Software KW - Somatosensory Cortex KW - Theta Rhythm KW - User-Computer Interface KW - Writing AB -

Brain-computer interfaces (BCIs) can be used for communication in writing without muscular activity or for learning to control seizures by voluntary regulation of brain signals such as the electroencephalogram (EEG). Three of five patients with epilepsy were able to spell their names with electrocorticogram (ECoG) signals derived from motor-related areas within only one or two training sessions. Imagery of finger or tongue movements was classified with support-vector classification of autoregressive coefficients derived from the ECoG signals. After training of the classifier, binary classification responses were used to select letters from a computer-generated menu. Offline analysis showed increased theta activity in the unsuccessful patients, whereas the successful patients exhibited dominant sensorimotor rhythms that they could control. The high spatial resolution and increased signal-to-noise ratio in ECoG signals, combined with short training periods, may offer an alternative for communication in complete paralysis, locked-in syndrome, and motor restoration.

VL - 13 UR - http://www.ncbi.nlm.nih.gov/pubmed/18495541 IS - 2 ER - TY - JOUR T1 - Decoding two-dimensional movement trajectories using electrocorticographic signals in humans. JF - J Neural Eng Y1 - 2007 A1 - Gerwin Schalk A1 - Kubánek, J A1 - Miller, John W A1 - Nicholas R Anderson A1 - Leuthardt, E C A1 - Ojemann, J G A1 - Limbrick, D A1 - Moran, D A1 - Lester A Gerhardt A1 - Jonathan Wolpaw KW - Adult KW - Algorithms KW - Arm KW - Brain Mapping KW - Cerebral Cortex KW - Electroencephalography KW - Evoked Potentials, Motor KW - Female KW - Humans KW - Male KW - Movement AB -

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.

VL - 4 UR - http://www.ncbi.nlm.nih.gov/pubmed/17873429 IS - 3 ER - TY - JOUR T1 - Electrocorticographic Frequency Alteration Mapping: A Clinical Technique for Mapping the Motor Cortex. JF - Neurosurgery Y1 - 2007 A1 - Leuthardt, E C A1 - Miller, John W A1 - Nicholas R Anderson A1 - Gerwin Schalk A1 - Dowling, Joshua A1 - Miller, John W A1 - Moran, D A1 - Ojemann, J G KW - Adult KW - Biological Clocks KW - Brain Mapping KW - Electric Stimulation KW - Electrodes, Implanted KW - Electroencephalography KW - Female KW - Hand KW - Humans KW - Male KW - Middle Aged KW - Motor Cortex KW - Oscillometry KW - Signal Processing, Computer-Assisted KW - Tongue AB -

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.

VL - 60 UR - http://www.ncbi.nlm.nih.gov/pubmed/17415162 IS - 4 Suppl 2 ER - TY - JOUR T1 - An MEG-based brain-computer interface (BCI). JF - Neuroimage Y1 - 2007 A1 - Mellinger, Jürgen A1 - Gerwin Schalk A1 - Christoph Braun A1 - Preissl, Hubert A1 - Rosenstiel, W. A1 - Niels Birbaumer A1 - Kübler, A. KW - Adult KW - Algorithms KW - Artifacts KW - Brain KW - Electroencephalography KW - Electromagnetic Fields KW - Electromyography KW - Feedback KW - Female KW - Foot KW - Hand KW - Head Movements KW - Humans KW - Magnetic Resonance Imaging KW - Magnetoencephalography KW - Male KW - Movement KW - Principal Component Analysis KW - Signal Processing, Computer-Assisted KW - User-Computer Interface AB -

Brain-computer interfaces (BCIs) allow for communicating intentions by mere brain activity, not involving muscles. Thus, BCIs may offer patients who have lost all voluntary muscle control the only possible way to communicate. Many recent studies have demonstrated that BCIs based on electroencephalography(EEG) can allow healthy and severely paralyzed individuals to communicate. While this approach is safe and inexpensive, communication is slow. Magnetoencephalography (MEG) provides signals with higher spatiotemporal resolution than EEG and could thus be used to explore whether these improved signal properties translate into increased BCI communication speed. In this study, we investigated the utility of an MEG-based BCI that uses voluntary amplitude modulation of sensorimotor mu and beta rhythms. To increase the signal-to-noise ratio, we present a simple spatial filtering method that takes the geometric properties of signal propagation in MEG into account, and we present methods that can process artifacts specifically encountered in an MEG-based BCI. Exemplarily, six participants were successfully trained to communicate binary decisions by imagery of limb movements using a feedback paradigm. Participants achieved significant mu rhythm self control within 32 min of feedback training. For a subgroup of three participants, we localized the origin of the amplitude modulated signal to the motor cortex. Our results suggest that an MEG-based BCI is feasible and efficient in terms of user training.

VL - 36 UR - http://www.ncbi.nlm.nih.gov/pubmed/17475511 IS - 3 ER - TY - JOUR T1 - Spectral Changes in Cortical Surface Potentials During Motor Movement. JF - J Neurosci Y1 - 2007 A1 - Miller, John W A1 - Leuthardt, E C A1 - Gerwin Schalk A1 - Rao, Rajesh P N A1 - Nicholas R Anderson A1 - Moran, D A1 - Miller, John W A1 - Ojemann, J G KW - Adult KW - Brain Mapping KW - Female KW - Humans KW - Male KW - Middle Aged KW - Motor Cortex KW - Movement AB -

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.

VL - 27 UR - http://www.ncbi.nlm.nih.gov/pubmed/17329441 IS - 9 ER - TY - JOUR T1 - Analysis of the correlation between local field potentials and neuronal firing rate in the motor cortex. JF - Conf Proc IEEE Eng Med Biol Soc Y1 - 2006 A1 - Wang, Yiwen A1 - Sanchez, Justin C A1 - Principe, Jose A1 - Mitzelfelt, Jeremiah D A1 - Gunduz, Aysegul KW - Action Potentials KW - Animals KW - Brain KW - Brain Mapping KW - Electric Stimulation KW - Electrodes KW - Evoked Potentials, Motor KW - Male KW - Models, Statistical KW - Motor Cortex KW - Neurons KW - Rats KW - Rats, Sprague-Dawley KW - Signal Processing, Computer-Assisted KW - Synaptic Transmission AB -

Neuronal firing rate has been the signal of choice for invasive motor brain machine interfaces (BMI). The use of local field potentials (LFP) in BMI experiments may provide additional dendritic information about movement intent and may improve performance. Here we study the time-varying amplitude modulated relationship between local field potentials (LFP) and single unit activity (SUA) in the motor cortex. We record LFP and SUA in the primary motor cortex of rats trained to perform a lever pressing task, and evaluate the correlation between pairs of peri-event time histograms (PETH) and movement evoked local field potentials (mEP) at the same electrode. Three different correlation coefficients were calculated and compared between the neuronal PETH and the magnitude and power of the mEP. Correlation as high as 0.7 for some neurons occurred between the PETH and the mEP magnitude. As expected, the correlations between the single trial LFP and SUV are much lower due to the inherent variability of both signals.

VL - 1 UR - http://www.ncbi.nlm.nih.gov/pubmed/17946745 ER - TY - JOUR T1 - Classifying EEG and ECoG signals without subject training for fast BCI implementation: comparison of nonparalyzed and completely paralyzed subjects. JF - IEEE Trans Neural Syst Rehabil Eng Y1 - 2006 A1 - Jeremy Jeremy Hill A1 - Lal, T.N A1 - Schröder, Michael A1 - Hinterberger, T. A1 - Wilhelm, Barbara A1 - Nijboer, F A1 - Mochty, Ursula A1 - Widman, Guido A1 - Elger, Christian A1 - Schölkopf, B A1 - Kübler, A. A1 - Niels Birbaumer KW - Algorithms KW - Artificial Intelligence KW - Cluster Analysis KW - Computer User Training KW - Electroencephalography KW - Evoked Potentials KW - Female KW - Humans KW - Imagination KW - Male KW - Middle Aged KW - Paralysis KW - Pattern Recognition, Automated KW - User-Computer Interface AB -

We summarize results from a series of related studies that aim to develop a motor-imagery-based brain-computer interface using a single recording session of electroencephalogram (EEG) or electrocorticogram (ECoG) signals for each subject. We apply the same experimental and analytical methods to 11 nonparalysed subjects (eight EEG, three ECoG), and to five paralyzed subjects (four EEG, one ECoG) who had been unable to communicate for some time. While it was relatively easy to obtain classifiable signals quickly from most of the nonparalyzed subjects, it proved impossible to classify the signals obtained from the paralyzed patients by the same methods. This highlights the fact that though certain BCI paradigms may work well with healthy subjects, this does not necessarily indicate success with the target user group. We outline possible reasons for this failure to transfer.

VL - 14 UR - http://www.ncbi.nlm.nih.gov/pubmed/16792289 IS - 2 ER - TY - JOUR T1 - ECoG factors underlying multimodal control of a brain-computer interface. JF - IEEE Trans Neural Syst Rehabil Eng Y1 - 2006 A1 - Adam J Wilson A1 - Felton, Elizabeth A A1 - Garell, P Charles A1 - Gerwin Schalk A1 - Williams, Justin C KW - Adult KW - Brain Mapping KW - Cerebral Cortex KW - Communication Aids for Disabled KW - Computer Peripherals KW - Evoked Potentials KW - Female KW - Humans KW - Imagination KW - Male KW - Man-Machine Systems KW - Neuromuscular Diseases KW - Systems Integration KW - User-Computer Interface KW - Volition AB -

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.

VL - 14 UR - http://www.ncbi.nlm.nih.gov/pubmed/16792305 IS - 2 ER - TY - JOUR T1 - Patients with ALS can use sensorimotor rhythms to operate a brain-computer interface. JF - Neurology Y1 - 2005 A1 - Kübler, A. A1 - Nijboer, F A1 - Mellinger, Jürgen A1 - Theresa M Vaughan A1 - Pawelzik, H A1 - Gerwin Schalk A1 - Dennis J. McFarland A1 - Niels Birbaumer A1 - Jonathan Wolpaw KW - Aged KW - Amyotrophic Lateral Sclerosis KW - Electroencephalography KW - Evoked Potentials, Motor KW - Evoked Potentials, Somatosensory KW - Female KW - Humans KW - Imagination KW - Male KW - Middle Aged KW - Motor Cortex KW - Movement KW - Paralysis KW - Photic Stimulation KW - Prostheses and Implants KW - Somatosensory Cortex KW - Treatment Outcome KW - User-Computer Interface AB -

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.

VL - 64 UR - http://www.ncbi.nlm.nih.gov/pubmed/15911809 IS - 10 ER - TY - JOUR T1 - A brain-computer interface using electrocorticographic signals in humans. JF - J Neural Eng Y1 - 2004 A1 - Leuthardt, E C A1 - Gerwin Schalk A1 - Jonathan Wolpaw A1 - Ojemann, J G A1 - Moran, D KW - Adult KW - Brain KW - Communication Aids for Disabled KW - Computer Peripherals KW - Diagnosis, Computer-Assisted KW - Electrodes, Implanted KW - Electroencephalography KW - Evoked Potentials KW - Female KW - Humans KW - Imagination KW - Male KW - Movement Disorders KW - User-Computer Interface AB -

Brain-computer interfaces (BCIs) enable users to control devices with electroencephalographic (EEG) activity from the scalp or with single-neuron activity from within the brain. Both methods have disadvantages: EEG has limited resolution and requires extensive training, while single-neuron recording entails significant clinical risks and has limited stability. We demonstrate here for the first time that electrocorticographic (ECoG) activity recorded from the surface of the brain can enable users to control a one-dimensional computer cursor rapidly and accurately. We first identified ECoG signals that were associated with different types of motor and speech imagery. Over brief training periods of 3-24 min, four patients then used these signals to master closed-loop control and to achieve success rates of 74-100% in a one-dimensional binary task. In additional open-loop experiments, we found that ECoG signals at frequencies up to 180 Hz encoded substantial information about the direction of two-dimensional joystick movements. Our results suggest that an ECoG-based BCI could provide for people with severe motor disabilities a non-muscular communication and control option that is more powerful than EEG-based BCIs and is potentially more stable and less traumatic than BCIs that use electrodes penetrating the brain.

VL - 1 UR - http://www.ncbi.nlm.nih.gov/pubmed/15876624 IS - 2 ER -