TY - JOUR T1 - Automated intraoperative central sulcus localization and somatotopic mapping using median nerve stimulation. JF - J Neural Eng Y1 - 2022 A1 - Xie, Tao A1 - Wu, Zehan A1 - Schalk, Gerwin A1 - Tong, Yusheng A1 - Vato, Alessandro A1 - Raviv, Nataly A1 - Guo, Qinglong A1 - Ye, Huanpeng A1 - Sheng, Xinjun A1 - Zhu, Xiangyang A1 - Peter Brunner A1 - Chen, Liang AB -

OBJECTIVE: Accurate identification of functional cortical regions is essential in neurological resection. The central sulcus (CS) is an important landmark that delineates functional cortical regions. Median nerve stimulation (MNS) is a standard procedure to identify the position of the CS intraoperatively. In this paper, we introduce an automated procedure that uses MNS to rapidly localize the CS and create functional somatotopic maps.

APPROACH: We recorded electrocorticographic signals from 13 patients who underwent MNS in the course of an awake craniotomy. We analyzed these signals to develop an automated procedure that determines the location of the CS and that also produces functional somatotopic maps.

MAIN RESULTS: The comparison between our automated method and visual inspection performed by the neurosurgeon shows that our procedure has a high sensitivity (89%) in identifying the CS. Further, we found substantial concordance between the functional somatotopic maps generated by our method and passive functional mapping (92% sensitivity).

SIGNIFICANCE: Our automated MNS-based method can rapidly localize the CS and create functional somatotopic maps without imposing additional burden on the clinical procedure. With additional development and validation, our method may lead to a diagnostic tool that guides neurosurgeon and reduces postoperative morbidity in patients undergoing resective brain surgery.

ER - TY - JOUR T1 - Dynamics of Oddball Sound Processing: Trial-by-Trial Modeling of ECoG Signals. JF - Front Hum Neurosci Y1 - 2022 A1 - Lecaignard, Françoise A1 - Bertrand, Raphaëlle A1 - Peter Brunner A1 - Caclin, Anne A1 - Schalk, Gerwin A1 - Mattout, Jérémie AB -

Recent computational models of perception conceptualize auditory oddball responses as signatures of a (Bayesian) learning process, in line with the influential view of the mismatch negativity (MMN) as a prediction error signal. Novel MMN experimental paradigms have put an emphasis on neurophysiological effects of manipulating regularity and predictability in sound sequences. This raises the question of the contextual adaptation of the learning process itself, which on the computational side speaks to the mechanisms of gain-modulated (or precision-weighted) prediction error. In this study using electrocorticographic (ECoG) signals, we manipulated the predictability of oddball sound sequences with two objectives: (i) Uncovering the computational process underlying trial-by-trial variations of the cortical responses. The fluctuations between trials, generally ignored by approaches based on averaged evoked responses, should reflect the learning involved. We used a general linear model (GLM) and Bayesian Model Reduction (BMR) to assess the respective contributions of experimental manipulations and learning mechanisms under probabilistic assumptions. (ii) To validate and expand on previous findings regarding the effect of changes in predictability using simultaneous EEG-MEG recordings. Our trial-by-trial analysis revealed only a few stimulus-responsive sensors but the measured effects appear to be consistent over subjects in both time and space. In time, they occur at the typical latency of the MMN (between 100 and 250 ms post-stimulus). In space, we found a dissociation between time-independent effects in more anterior temporal locations and time-dependent (learning) effects in more posterior locations. However, we could not observe any clear and reliable effect of our manipulation of predictability modulation onto the above learning process. Overall, these findings clearly demonstrate the potential of trial-to-trial modeling to unravel perceptual learning processes and their neurophysiological counterparts.

VL - 15 ER - TY - JOUR T1 - A neural population selective for song in human auditory cortex JF - Current Biology Y1 - 2022 A1 - Sam V. Norman-Haignere A1 - Jenelle Feather A1 - Dana Boebinger A1 - Peter Brunner A1 - Anthony Ritaccio A1 - Josh H. McDermott A1 - Gerwin Schalk A1 - Nancy Kanwisher KW - Auditory Cortex KW - component KW - ECoG KW - Electrocorticography KW - fMRI KW - music KW - natural sounds KW - song KW - Speech KW - voice AB - Summary How is music represented in the brain? While neuroimaging has revealed some spatial segregation between responses to music versus other sounds, little is known about the neural code for music itself. To address this question, we developed a method to infer canonical response components of human auditory cortex using intracranial responses to natural sounds, and further used the superior coverage of fMRI to map their spatial distribution. The inferred components replicated many prior findings, including distinct neural selectivity for speech and music, but also revealed a novel component that responded nearly exclusively to music with singing. Song selectivity was not explainable by standard acoustic features, was located near speech- and music-selective responses, and was also evident in individual electrodes. These results suggest that representations of music are fractionated into subpopulations selective for different types of music, one of which is specialized for the analysis of song. VL - 32 UR - https://www.sciencedirect.com/science/article/pii/S0960982222001312 ER - 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 - iEEGview: an open-source multifunction GUI-based Matlab toolbox for localization and visualization of human intracranial electrodes. JF - J Neural Eng Y1 - 2019 A1 - Li, Guangye A1 - Jiang, Shize A1 - Chen, Chen A1 - Peter Brunner A1 - Wu, Zehan A1 - Schalk, Gerwin A1 - Chen, Liang A1 - Zhang, Dingguo KW - Brain KW - Brain Mapping KW - Electrocorticography KW - Electrodes, Implanted KW - Electroencephalography KW - Humans KW - Magnetic Resonance Imaging AB -

OBJECTIVE: The precise localization of intracranial electrodes is a fundamental step relevant to the analysis of intracranial electroencephalography (iEEG) recordings in various fields. With the increasing development of iEEG studies in human neuroscience, higher requirements have been posed on the localization process, resulting in urgent demand for more integrated, easy-operation and versatile tools for electrode localization and visualization. With the aim of addressing this need, we develop an easy-to-use and multifunction toolbox called iEEGview, which can be used for the localization and visualization of human intracranial electrodes.

APPROACH: iEEGview is written in Matlab scripts and implemented with a GUI. From the GUI, by taking only pre-implant MRI and post-implant CT images as input, users can directly run the full localization pipeline including brain segmentation, image co-registration, electrode reconstruction, anatomical information identification, activation map generation and electrode projection from native brain space into common brain space for group analysis. Additionally, iEEGview implements methods for brain shift correction, visual location inspection on MRI slices and computation of certainty index in anatomical label assignment.

MAIN RESULTS: All the introduced functions of iEEGview work reliably and successfully, and are tested by images from 28 human subjects implanted with depth and/or subdural electrodes.

SIGNIFICANCE: iEEGview is the first public Matlab GUI-based software for intracranial electrode localization and visualization that holds integrated capabilities together within one pipeline. iEEGview promotes convenience and efficiency for the localization process, provides rich localization information for further analysis and offers solutions for addressing raised technical challenges. Therefore, it can serve as a useful tool in facilitating iEEG studies.

VL - 17 IS - 1 ER - TY - JOUR T1 - A quantitative method for evaluating cortical responses to electrical stimulation JF - Journal of Neuroscience Methods Y1 - 2019 A1 - Lawrence J. Crowther A1 - Peter Brunner A1 - Christoph Kapeller A1 - Christoph Guger A1 - Kyousuke Kamada A1 - Marjorie E. Bunch A1 - Bridget K. Frawley A1 - Timothy M. Lynch A1 - Anthony L. Ritaccio A1 - Gerwin Schalk KW - Connectivity KW - Cortico-cortical evoked potentials KW - Electrical stimulation KW - Electrocorticography AB - Background Electrical stimulation of the cortex using subdurally implanted electrodes can causally reveal structural connectivity by eliciting cortico-cortical evoked potentials (CCEPs). While many studies have demonstrated the potential value of CCEPs, the methods to evaluate them were often relatively subjective, did not consider potential artifacts, and did not lend themselves to systematic scientific investigations. New method We developed an automated and quantitative method called SIGNI (Stimulation-Induced Gamma-based Network Identification) to evaluate cortical population-level responses to electrical stimulation that minimizes the impact of electrical artifacts. We applied SIGNI to electrocorticographic (ECoG) data from eight human subjects who were implanted with a total of 978 subdural electrodes. Across the eight subjects, we delivered 92 trains of approximately 200 discrete electrical stimuli each (amplitude 4–15 mA) to a total of 64 electrode pairs. Results We verified SIGNI's efficacy by demonstrating a relationship between the magnitude of evoked cortical activity and stimulation amplitude, as well as between the latency of evoked cortical activity and the distance from the stimulated locations. Conclusions SIGNI reveals the timing and amplitude of cortical responses to electrical stimulation as well as the structural connectivity supporting these responses. With these properties, it enables exploration of new and important questions about the neurophysiology of cortical communication and may also be useful for pre-surgical planning. VL - 311 UR - http://www.sciencedirect.com/science/article/pii/S0165027018302796 ER - TY - CHAP T1 - BCI Software T2 - Brain–Computer Interfaces Handbook: Technological and Theoretical Advances Y1 - 2018 A1 - Peter Brunner A1 - Schalk, Gerwin JF - Brain–Computer Interfaces Handbook: Technological and Theoretical Advances ER - TY - Generic T1 - Creating an eyes-closed binary SSVEP-based brain-computer interface (BCI) for the bedside: A comparison of foveal centered and off-centered stimulus presentation Y1 - 2018 A1 - T. M. Vaughan A1 - M. Aslam A1 - B. Zoltan A1 - Peter Brunner A1 - J. J. Norton A1 - C. S. Carmack A1 - D. J. Zeitlin A1 - Jonathan Wolpaw ER - TY - Generic T1 - Creating an eyes-closed binary SSVEP-based brain-computer interface (BCI) for the bedside: A comparison of foveal centered and off-centered stimulus presentation T2 - Program No. 225.17. 2018 Neuroscience Meeting Planner. San Diego, CA: Society for Neuroscience. Online. Y1 - 2018 A1 - T.M. Vaughan A1 - M. Aslam A1 - B. Zoltan A1 - Peter Brunner A1 - J. J. Norton A1 - C. S. Carmack A1 - D. J. Zeitlin A1 - Jonathan Wolpaw JF - Program No. 225.17. 2018 Neuroscience Meeting Planner. San Diego, CA: Society for Neuroscience. Online. CY - San Diego, CA ER - TY - JOUR T1 - Electrical Stimulation Mapping of the Brain: Basic Principles and Emerging Alternatives JF - Journal of Clinical Neurophysiology Y1 - 2018 A1 - Ritaccio, A A1 - Peter Brunner A1 - Schalk, G KW - Brain Mapping KW - Corticocortical-evoked potentials KW - electrical stimulation mapping KW - Electrocorticography KW - Functional localization KW - Passive gamma mapping AB - The application of electrical stimulation mapping (ESM) of the brain for clinical use is approximating a century. Despite this long-standing history, the value of ESM for guiding surgical resections and sparing eloquent cortex is documented largely by small retrospective studies, and ESM protocols are largely inherited and lack standardization. Although models are imperfect and mechanisms are complex, the probabilistic causality of ESM has guaranteed its perpetuation into the 21st century. At present, electrical stimulation of cortical tissue is being revisited for network connectivity. In addition, noninvasive and passive mapping techniques are rapidly evolving to complement and potentially replace ESM in specific clinical situations. Lesional and epilepsy neurosurgery cases now offer different opportunities for multimodal functional assessments. VL - 35 UR - https://journals.lww.com/clinicalneurophys/Abstract/2018/03000/Electrical_Stimulation_Mapping_of_the_Brain__.2.aspx IS - 2 ER - TY - Generic T1 - Instantaneous voltage of electroencephalographic oscillatory activity: An alternative to power and phase measurements T2 - Program No. 125.17. 2018 Neuroscience Meeting Planner. San Diego, CA: Society for Neuroscience. Online. Y1 - 2018 A1 - M. Adamek A1 - Peter Brunner A1 - L. Moheimanian A1 - R. Scherer A1 - G. Schalk JF - Program No. 125.17. 2018 Neuroscience Meeting Planner. San Diego, CA: Society for Neuroscience. Online. ER - TY - Generic T1 - Instantaneous voltage of electroencephalographic oscillatory activity: An alternative to power and phase measurements T2 - Program No. 125.17. 2018 Neuroscience Meeting Planner. San Diego, CA: Society for Neuroscience. Online. Y1 - 2018 A1 - M. Adamek A1 - Peter Brunner A1 - L. Moheimanian A1 - R. Scherer A1 - G. Schalk JF - Program No. 125.17. 2018 Neuroscience Meeting Planner. San Diego, CA: Society for Neuroscience. Online. CY - San Diego, CA ER - TY - JOUR T1 - Passive functional mapping of receptive language areas using electrocorticographic signals JF - Clinical Neurophysiology Y1 - 2018 A1 - J.R. Swift A1 - W.G. Coon A1 - C. Guger A1 - Peter Brunner A1 - M. Bunch A1 - T. Lynch A1 - B. Frawley A1 - A.L. Ritaccio A1 - G. Schalk KW - ECoG KW - Electrocorticography KW - functional mapping KW - Intracranial KW - Receptive language VL - 129 UR - http://www.sciencedirect.com/science/article/pii/S1388245718312288 ER - TY - Generic T1 - Rapid Identification of Cortical Connectivity During Functional Mapping T2 - American Epilepsy Society 72nd Annual Meeting Y1 - 2018 A1 - Lawrence J. Crowther A1 - Peter Brunner A1 - Anthony L. Ritaccio A1 - Gerwin Schalk JF - American Epilepsy Society 72nd Annual Meeting CY - New Orleans, LA ER - TY - JOUR T1 - Spatiotemporal dynamics of word retrieval in speech production revealed by cortical high-frequency band activity. JF - Proceedings of the National Academy of Sciences of the United States of America Y1 - 2017 A1 - Riès, Stephanie K. A1 - Dhillon, Rummit K. A1 - Clarke, Alex A1 - King-Stephens, David A1 - Laxer, Kenneth D. A1 - Weber, Peter B. A1 - Kuperman, Rachel A. A1 - Auguste, Kurtis I. A1 - Peter Brunner A1 - Gerwin Schalk A1 - Lin, Jack J. A1 - Parvizi, Josef A1 - Crone, Nathan E. A1 - Dronkers, Nina F. A1 - Robert T. Knight AB - Word retrieval is core to language production and relies on complementary processes: the rapid activation of lexical and conceptual representations and word selection, which chooses the correct word among semantically related competitors. Lexical and conceptual activation is measured by semantic priming. In contrast, word selection is indexed by semantic interference and is hampered in semantically homogeneous (HOM) contexts. We examined the spatiotemporal dynamics of these complementary processes in a picture naming task with blocks of semantically heterogeneous (HET) or HOM stimuli. We used electrocorticography data obtained from frontal and temporal cortices, permitting detailed spatiotemporal analysis of word retrieval processes. A semantic interference effect was observed with naming latencies longer in HOM versus HET blocks. Cortical response strength as indexed by high-frequency band (HFB) activity (70-150 Hz) amplitude revealed effects linked to lexical-semantic activation and word selection observed in widespread regions of the cortical mantle. Depending on the subsecond timing and cortical region, HFB indexed semantic interference (i.e., more activity in HOM than HET blocks) or semantic priming effects (i.e., more activity in HET than HOM blocks). These effects overlapped in time and space in the left posterior inferior temporal gyrus and the left prefrontal cortex. The data do not support a modular view of word retrieval in speech production but rather support substantial overlap of lexical-semantic activation and word selection mechanisms in the brain. UR - http://www.ncbi.nlm.nih.gov/pubmed/28533406 ER - TY - JOUR T1 - Alpha power indexes task-related networks on large and small scales: A multimodal ECoG study in humans and a non-human primate. JF - NeuroImage Y1 - 2016 A1 - de Pesters, A. A1 - Coon, W. G. A1 - Peter Brunner A1 - Gunduz, A. A1 - A L Ritaccio A1 - Brunet, N. M. A1 - de Weerd, P. A1 - Roberts, M. J. A1 - Oostenveld, R. A1 - Fries, P. A1 - Gerwin Schalk AB - Performing different tasks, such as generating motor movements or processing sensory input, requires the recruitment of specific networks of neuronal populations. Previous studies suggested that power variations in the alpha band (8-12Hz) may implement such recruitment of task-specific populations by increasing cortical excitability in task-related areas while inhibiting population-level cortical activity in task-unrelated areas (Klimesch et al., 2007; Jensen and Mazaheri, 2010). However, the precise temporal and spatial relationships between the modulatory function implemented by alpha oscillations and population-level cortical activity remained undefined. Furthermore, while several studies suggested that alpha power indexes task-related populations across large and spatially separated cortical areas, it was largely unclear whether alpha power also differentially indexes smaller networks of task-related neuronal populations. Here we addressed these questions by investigating the temporal and spatial relationships of electrocorticographic (ECoG) power modulations in the alpha band and in the broadband gamma range (70-170Hz, indexing population-level activity) during auditory and motor tasks in five human subjects and one macaque monkey. In line with previous research, our results confirm that broadband gamma power accurately tracks task-related behavior and that alpha power decreases in task-related areas. More importantly, they demonstrate that alpha power suppression lags population-level activity in auditory areas during the auditory task, but precedes it in motor areas during the motor task. This suppression of alpha power in task-related areas was accompanied by an increase in areas not related to the task. In addition, we show for the first time that these differential modulations of alpha power could be observed not only across widely distributed systems (e.g., motor vs. auditory system), but also within the auditory system. Specifically, alpha power was suppressed in the locations within the auditory system that most robustly responded to particular sound stimuli. Altogether, our results provide experimental evidence for a mechanism that preferentially recruits task-related neuronal populations by increasing cortical excitability in task-related cortical areas and decreasing cortical excitability in task-unrelated areas. This mechanism is implemented by variations in alpha power and is common to humans and the non-human primate under study. These results contribute to an increasingly refined understanding of the mechanisms underlying the selection of the specific neuronal populations required for task execution. VL - 134 UR - http://www.ncbi.nlm.nih.gov/pubmed/27057960 ER - TY - JOUR T1 - Differential roles of high gamma and local motor potentials for movement preparation and execution JF - Brain-Computer Interfaces Y1 - 2016 A1 - Gunduz, Aysegul A1 - Peter Brunner A1 - Sharma, Mohit A1 - Leuthardt, Eric C. A1 - Ritaccio, Anthony L. A1 - Pesaran, Bijan A1 - Schalk, Gerwin KW - BCI KW - brain-computer interfaces KW - ECoG KW - Electrocorticography KW - sensorimotor systems AB - Determining a person’s intent, such as the planned direction of their movement, directly from their cortical activity could support important applications such as brain-computer interfaces (BCIs). Continuing development of improved BCI systems requires a better understanding of how the brain prepares for and executes movements. To contribute to this understanding, we recorded surface cortical potentials (electrocorticographic signals; ECoG) in 11 human subjects performing a delayed center-out task to establish the differential role of high gamma activity (HGA) and the local motor potential (LMP) as a function of time and anatomical area during movement preparation and execution. High gamma modulations mostly confirm previous findings of sensorimotor cortex involvement, whereas modulations in LMPs are observed in prefrontal cortices. These modulations include directional information during movement planning as well as execution. Our results suggest that sampling signals from these widely distributed cortical areas improves decoding accuracy. VL - 3 IS - 2 ER - TY - JOUR T1 - Intraoperative mapping of expressive language cortex using passive real-time electrocorticography. JF - Epilepsy & behavior case reports Y1 - 2016 A1 - Taplin, AmiLyn M. A1 - de Pesters, Adriana A1 - Peter Brunner A1 - Hermes, Dora A1 - Dalfino, John C. A1 - Adamo, Matthew A. A1 - A L Ritaccio A1 - Gerwin Schalk AB - In this case report, we investigated the utility and practicality of passive intraoperative functional mapping of expressive language cortex using high-resolution electrocorticography (ECoG). The patient presented here experienced new-onset seizures caused by a medium-grade tumor in very close proximity to expressive language regions. In preparation of tumor resection, the patient underwent multiple functional language mapping procedures. We examined the relationship of results obtained with intraoperative high-resolution ECoG, extraoperative ECoG utilizing a conventional subdural grid, extraoperative electrical cortical stimulation (ECS) mapping, and functional magnetic resonance imaging (fMRI). Our results demonstrate that intraoperative mapping using high-resolution ECoG is feasible and, within minutes, produces results that are qualitatively concordant to those achieved by extraoperative mapping modalities. They also suggest that functional language mapping of expressive language areas with ECoG may prove useful in many intraoperative conditions given its time efficiency and safety. Finally, they demonstrate that integration of results from multiple functional mapping techniques, both intraoperative and extraoperative, may serve to improve the confidence in or precision of functional localization when pathology encroaches upon eloquent language cortex. VL - 5 UR - http://www.ncbi.nlm.nih.gov/pubmed/27408802 ER - TY - JOUR T1 - Neural correlate of the construction of sentence meaning. JF - Proceedings of the National Academy of Sciences of the United States of America Y1 - 2016 A1 - Fedorenko, Evelina A1 - Scott, Terri L. A1 - Peter Brunner A1 - Coon, William G. A1 - Pritchett, Brianna A1 - Gerwin Schalk A1 - Kanwisher, Nancy AB - The neural processes that underlie your ability to read and understand this sentence are unknown. Sentence comprehension occurs very rapidly, and can only be understood at a mechanistic level by discovering the precise sequence of underlying computational and neural events. However, we have no continuous and online neural measure of sentence processing with high spatial and temporal resolution. Here we report just such a measure: intracranial recordings from the surface of the human brain show that neural activity, indexed by $\gamma$-power, increases monotonically over the course of a sentence as people read it. This steady increase in activity is absent when people read and remember nonword-lists, despite the higher cognitive demand entailed, ruling out accounts in terms of generic attention, working memory, and cognitive load. Response increases are lower for sentence structure without meaning (``Jabberwocky'' sentences) and word meaning without sentence structure (word-lists), showing that this effect is not explained by responses to syntax or word meaning alone. Instead, the full effect is found only for sentences, implicating compositional processes of sentence understanding, a striking and unique feature of human language not shared with animal communication systems. This work opens up new avenues for investigating the sequence of neural events that underlie the construction of linguistic meaning. VL - 113 UR - http://www.ncbi.nlm.nih.gov/pubmed/27671642 ER - TY - JOUR T1 - Oscillatory phase modulates the timing of neuronal activations and resulting behavior. JF - NeuroImage Y1 - 2016 A1 - Coon, W. G. A1 - Gunduz, A. A1 - Peter Brunner A1 - A L Ritaccio A1 - Pesaran, B. A1 - Gerwin Schalk AB - Human behavioral response timing is highly variable from trial to trial. While it is generally understood that behavioral variability must be due to trial-by-trial variations in brain function, it is still largely unknown which physiological mechanisms govern the timing of neural activity as it travels through networks of neuronal populations, and how variations in the timing of neural activity relate to variations in the timing of behavior. In our study, we submitted recordings from the cortical surface to novel analytic techniques to chart the trajectory of neuronal population activity across the human cortex in single trials, and found joint modulation of the timing of this activity and of consequent behavior by neuronal oscillations in the alpha band (8-12Hz). Specifically, we established that the onset of population activity tends to occur during the trough of oscillatory activity, and that deviations from this preferred relationship are related to changes in the timing of population activity and the speed of the resulting behavioral response. These results indicate that neuronal activity incurs variable delays as it propagates across neuronal populations, and that the duration of each delay is a function of the instantaneous phase of oscillatory activity. We conclude that the results presented in this paper are supportive of a general model for variability in the effective speed of information transmission in the human brain and for variability in the timing of human behavior. VL - 133 UR - http://www.ncbi.nlm.nih.gov/pubmed/26975551 ER - TY - JOUR T1 - Spatio-Temporal Progression of Cortical Activity Related to Continuous Overt and Covert Speech Production in a Reading Task. JF - PloS one Y1 - 2016 A1 - Brumberg, Jonathan S. A1 - Krusienski, Dean J. A1 - Chakrabarti, Shreya A1 - Gunduz, Aysegul A1 - Peter Brunner A1 - A L Ritaccio A1 - Gerwin Schalk AB - How the human brain plans, executes, and monitors continuous and fluent speech has remained largely elusive. For example, previous research has defined the cortical locations most important for different aspects of speech function, but has not yet yielded a definition of the temporal progression of involvement of those locations as speech progresses either overtly or covertly. In this paper, we uncovered the spatio-temporal evolution of neuronal population-level activity related to continuous overt speech, and identified those locations that shared activity characteristics across overt and covert speech. Specifically, we asked subjects to repeat continuous sentences aloud or silently while we recorded electrical signals directly from the surface of the brain (electrocorticography (ECoG)). We then determined the relationship between cortical activity and speech output across different areas of cortex and at sub-second timescales. The results highlight a spatio-temporal progression of cortical involvement in the continuous speech process that initiates utterances in frontal-motor areas and ends with the monitoring of auditory feedback in superior temporal gyrus. Direct comparison of cortical activity related to overt versus covert conditions revealed a common network of brain regions involved in speech that may implement orthographic and phonological processing. Our results provide one of the first characterizations of the spatiotemporal electrophysiological representations of the continuous speech process, and also highlight the common neural substrate of overt and covert speech. These results thereby contribute to a refined understanding of speech functions in the human brain. VL - 11 UR - http://www.ncbi.nlm.nih.gov/pubmed/27875590 ER - TY - JOUR T1 - Word pair classification during imagined speech using direct brain recordings. JF - Scientific reports Y1 - 2016 A1 - Martin, Stéphanie A1 - Peter Brunner A1 - Iturrate, Iñaki A1 - Millán, José Del R. A1 - Gerwin Schalk A1 - Robert T. Knight A1 - Pasley, Brian N. AB - People that cannot communicate due to neurological disorders would benefit from an internal speech decoder. Here, we showed the ability to classify individual words during imagined speech from electrocorticographic signals. In a word imagery task, we used high gamma (70-150þinspaceHz) time features with a support vector machine model to classify individual words from a pair of words. To account for temporal irregularities during speech production, we introduced a non-linear time alignment into the SVM kernel. Classification accuracy reached 88% in a two-class classification framework (50% chance level), and average classification accuracy across fifteen word-pairs was significant across five subjects (meanþinspace=þinspace58%; pþinspace<þinspace0.05). We also compared classification accuracy between imagined speech, overt speech and listening. As predicted, higher classification accuracy was obtained in the listening and overt speech conditions (meanþinspace=þinspace89% and 86%, respectively; pþinspace<þinspace0.0001), where speech stimuli were directly presented. The results provide evidence for a neural representation for imagined words in the temporal lobe, frontal lobe and sensorimotor cortex, consistent with previous findings in speech perception and production. These data represent a proof of concept study for basic decoding of speech imagery, and delineate a number of key challenges to usage of speech imagery neural representations for clinical applications. VL - 6 UR - http://www.ncbi.nlm.nih.gov/pubmed/27165452 ER - TY - JOUR T1 - Brain-to-text: Decoding spoken sentences from phone representations in the brain. JF - Journal of Neural Engineering Y1 - 2015 A1 - Herff, C. A1 - Heger, D. A1 - Pesters, Adriana de A1 - Telaar, D. A1 - Peter Brunner A1 - Gerwin Schalk A1 - Schultz, T. KW - automatic speech recognition KW - brain-computer interface KW - broadband gamma KW - ECoG KW - Electrocorticography KW - pattern recognition KW - speech decoding KW - speech production AB - It has long been speculated whether communication between humans and machines based on natural speech related cortical activity is possible. Over the past decade, studies have suggested that it is feasible to recognize isolated aspects of speech from neural signals, such as auditory features, phones or one of a few isolated words. However, until now it remained an unsolved challenge to decode continuously spoken speech from the neural substrate associated with speech and language processing. Here, we show for the first time that continuously spoken speech can be decoded into the expressed words from intracranial electrocorticographic (ECoG) recordings.Specifically, we implemented a system, which we call Brain-To-Text that models single phones, employs techniques from automatic speech recognition (ASR), and thereby transforms brain activity while speaking into the corresponding textual representation. Our results demonstrate that our system can achieve word error rates as low as 25% and phone error rates below 50%. Additionally, our approach contributes to the current understanding of the neural basis of continuous speech production by identifying those cortical regions that hold substantial information about individual phones. In conclusion, the Brain-To- Text system described in this paper represents an important step toward human-machine communication based on imagined speech. UR - http://journal.frontiersin.org/article/10.3389/fnins.2015.00217/abstract ER - TY - JOUR T1 - The effects of spatial filtering and artifacts on electrocorticographic signals. JF - Journal of neural engineering Y1 - 2015 A1 - Liu, Y. A1 - Coon, W. G. A1 - de Pesters, A. A1 - Peter Brunner A1 - Gerwin Schalk KW - Young Adult AB - Electrocorticographic (ECoG) signals contain noise that is common to all channels and noise that is specific to individual channels. Most published ECoG studies use common average reference (CAR) spatial filters to remove common noise, but CAR filters may introduce channel-specific noise into other channels. To address this concern, scientists often remove artifactual channels prior to data analysis. However, removing these channels depends on expert-based labeling and may also discard useful data. Thus, the effects of spatial filtering and artifacts on ECoG signals have been largely unknown. This study aims to quantify these effects and thereby address this gap in knowledge. VL - 12 UR - http://www.ncbi.nlm.nih.gov/pubmed/26268446 ER - TY - JOUR T1 - Electrocorticographic representations of segmental features in continuous speech. JF - Front Hum Neurosci Y1 - 2015 A1 - Lotte, Fabien A1 - Jonathan S Brumberg A1 - Peter Brunner A1 - Gunduz, Aysegul A1 - A L Ritaccio A1 - Guan, Cuntai A1 - Gerwin Schalk KW - electrocorticography (ECoG) KW - manner of articulation KW - place of articulation KW - speech processing KW - voicing AB - Acoustic speech output results from coordinated articulation of dozens of muscles, bones and cartilages of the vocal mechanism. While we commonly take the fluency and speed of our speech productions for granted, the neural mechanisms facilitating the requisite muscular control are not completely understood. Previous neuroimaging and electrophysiology studies of speech sensorimotor control has typically concentrated on speech sounds (i.e., phonemes, syllables and words) in isolation; sentence-length investigations have largely been used to inform coincident linguistic processing. In this study, we examined the neural representations of segmental features (place and manner of articulation, and voicing status) in the context of fluent, continuous speech production. We used recordings from the cortical surface [electrocorticography (ECoG)] to simultaneously evaluate the spatial topography and temporal dynamics of the neural correlates of speech articulation that may mediate the generation of hypothesized gestural or articulatory scores. We found that the representation of place of articulation involved broad networks of brain regions during all phases of speech production: preparation, execution and monitoring. In contrast, manner of articulation and voicing status were dominated by auditory cortical responses after speech had been initiated. These results provide a new insight into the articulatory and auditory processes underlying speech production in terms of their motor requirements and acoustic correlates. VL - 9 UR - http://www.ncbi.nlm.nih.gov/pubmed/25759647 ER - TY - JOUR T1 - Identifying the Attended Speaker Using Electrocorticographic (ECoG) Signals. JF - Journal of Neural Engineering Y1 - 2015 A1 - Dijkstra, K. A1 - Peter Brunner A1 - Gunduz, Aysegul A1 - Coon, W.G. A1 - A L Ritaccio A1 - Farquhar, Jason A1 - Gerwin Schalk KW - auditory attention KW - Brain-computer interface (BCI) KW - Cocktail Party KW - electrocorticography (ECoG) AB - People affected by severe neuro-degenerative diseases (e.g., late-stage amyotrophic lateral sclerosis (ALS) or locked-in syndrome) eventually lose all muscular control. Thus, they cannot use traditional assistive communication devices that depend on muscle control, or brain-computer interfaces (BCIs) that depend on the ability to control gaze. While auditory and tactile BCIs can provide communication to such individuals, their use typically entails an artificial mapping between the stimulus and the communication intent. This makes these BCIs difficult to learn and use. In this study, we investigated the use of selective auditory attention to natural speech as an avenue for BCI communication. In this approach, the user communicates by directing his/her attention to one of two simultaneously presented speakers. We used electrocorticographic (ECoG) signals in the gamma band (70–170 Hz) to infer the identity of attended speaker, thereby removing the need to learn such an artificial mapping. Our results from twelve human subjects show that a single cortical location over superior temporal gyrus or pre-motor cortex is typically sufficient to identify the attended speaker within 10 s and with 77% accuracy (50% accuracy due to chance). These results lay the groundwork for future studies that may determine the real-time performance of BCIs based on selective auditory attention to speech. UR - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4776341/ ER - TY - CHAP T1 - Towards an Auditory Attention BCI T2 - Brain-Computer Interface Research: A State-of-the-Art Summary Y1 - 2015 A1 - Peter Brunner A1 - Dijkstra, K. A1 - Coon, W.G. A1 - Mellinger, Jürgen A1 - A L Ritaccio A1 - Gerwin Schalk AB - People affected by severe neuro-degenerative diseases (e.g., late-stage amyotrophic lateral sclerosis (ALS) or locked-in syndrome) eventually lose all muscular control and are no longer able to gesture or speak. For this population, an auditory BCI is one of only a few remaining means of communication. All currently used auditory BCIs require a relatively artificial mapping between a stimulus and a communication output. This mapping is cumbersome to learn and use. Recent studies suggest that electrocorticographic (ECoG) signals in the gamma band (i.e., 70–170 Hz) can be used to infer the identity of auditory speech stimuli, effectively removing the need to learn such an artificial mapping. However, BCI systems that use this physiological mechanism for communication purposes have not yet been described. In this study, we explore this possibility by implementing a BCI2000-based real-time system that uses ECoG signals to identify the attended speaker. JF - Brain-Computer Interface Research: A State-of-the-Art Summary PB - Springer International Publishing CY - New York City, NY SN - 978-3-319-25188-2 UR - http://link.springer.com/chapter/10.1007%2F978-3-319-25190-5_4 ER - TY - JOUR T1 - Assessing dynamics, spatial scale, and uncertainty in task-related brain network analyses. JF - Frontiers in Computational Neuroscience Y1 - 2014 A1 - Stephen, Emily P A1 - Lepage, Kyle Q A1 - Eden, Uri T A1 - Peter Brunner A1 - Gerwin Schalk A1 - Jonathan S Brumberg A1 - Guenther, Frank H A1 - Kramer, Mark A KW - canonical correlation KW - coherence KW - ECoG KW - EEG KW - functional connectivity KW - MEG AB - The brain is a complex network of interconnected elements, whose interactions evolve dynamically in time to cooperatively perform specific functions. A common technique to probe these interactions involves multi-sensor recordings of brain activity during a repeated task. Many techniques exist to characterize the resulting task-related activity, including establishing functional networks, which represent the statistical associations between brain areas. Although functional network inference is commonly employed to analyze neural time series data, techniques to assess the uncertainty—both in the functional network edges and the corresponding aggregate measures of network topology—are lacking. To address this, we describe a statistically principled approach for computing uncertainty in functional networks and aggregate network measures in task-related data. The approach is based on a resampling procedure that utilizes the trial structure common in experimental recordings. We show in simulations that this approach successfully identifies functional networks and associated measures of confidence emergent during a task in a variety of scenarios, including dynamically evolving networks. In addition, we describe a principled technique for establishing functional networks based on predetermined regions of interest using canonical correlation. Doing so provides additional robustness to the functional network inference. Finally, we illustrate the use of these methods on example invasive brain voltage recordings collected during an overt speech task. The general strategy described here—appropriate for static and dynamic network inference and different statistical measures of coupling—permits the evaluation of confidence in network measures in a variety of settings common to neuroscience. VL - 8 UR - http://www.ncbi.nlm.nih.gov/pubmed/24678295 IS - 31 ER - TY - JOUR T1 - Decoding spectrotemporal features of overt and covert speech from the human cortex. JF - Frontiers in Neuroengineering Y1 - 2014 A1 - Martin, Stéphanie A1 - Peter Brunner A1 - Holdgraf, Chris A1 - Heinze, Hans-Jochen A1 - Nathan E. Crone A1 - Rieger, Jochem A1 - Gerwin Schalk A1 - Robert T. Knight A1 - Pasley, Brian N. KW - covert speech KW - decoding model KW - Electrocorticography KW - pattern recognition KW - speech production AB - Auditory perception and auditory imagery have been shown to activate overlapping brain regions. We hypothesized that these phenomena also share a common underlying neural representation. To assess this, we used electrocorticography intracranial recordings from epileptic patients performing an out loud or a silent reading task. In these tasks, short stories scrolled across a video screen in two conditions: subjects read the same stories both aloud (overt) and silently (covert). In a control condition the subject remained in a resting state. We first built a high gamma (70–150 Hz) neural decoding model to reconstruct spectrotemporal auditory features of self-generated overt speech. We then evaluated whether this same model could reconstruct auditory speech features in the covert speech condition. Two speech models were tested: a spectrogram and a modulation-based feature space. For the overt condition, reconstruction accuracy was evaluated as the correlation between original and predicted speech features, and was significant in each subject (p < 0.00001; paired two-sample t-test). For the covert speech condition, dynamic time warping was first used to realign the covert speech reconstruction with the corresponding original speech from the overt condition. Reconstruction accuracy was then evaluated as the correlation between original and reconstructed speech features. Covert reconstruction accuracy was compared to the accuracy obtained from reconstructions in the baseline control condition. Reconstruction accuracy for the covert condition was significantly better than for the control condition (p < 0.005; paired two-sample t-test). The superior temporal gyrus, pre- and post-central gyrus provided the highest reconstruction information. The relationship between overt and covert speech reconstruction depended on anatomy. These results provide evidence that auditory representations of covert speech can be reconstructed from models that are built from an overt speech data set, supporting a partially shared neural substrate. VL - 7 UR - http://www.ncbi.nlm.nih.gov/pubmed/24904404 IS - 14 ER - TY - JOUR T1 - Proceedings of the Fifth International Workshop on Advances in Electrocorticography. JF - Epilepsy Behav Y1 - 2014 A1 - A L Ritaccio A1 - Peter Brunner A1 - Gunduz, Aysegul A1 - Hermes, Dora A1 - Hirsch, Lawrence J A1 - Jacobs, Joshua A1 - Kamada, Kyousuke A1 - Kastner, Sabine A1 - Robert T. Knight A1 - Lesser, Ronald P A1 - Miller, Kai A1 - Sejnowski, Terrence A1 - Worrell, Gregory A1 - Gerwin Schalk KW - Brain Mapping KW - brain-computer interface KW - electrical stimulation mapping KW - Electrocorticography KW - functional mapping KW - Gamma-frequency electroencephalography KW - High-frequency oscillations KW - Neuroprosthetics KW - Seizure detection KW - Subdural grid AB -

The Fifth International Workshop on Advances in Electrocorticography convened in San Diego, CA, on November 7-8, 2013. Advancements in methodology, implementation, and commercialization across both research and in the interval year since the last workshop were the focus of the gathering. Electrocorticography (ECoG) is now firmly established as a preferred signal source for advanced research in functional, cognitive, and neuroprosthetic domains. Published output in ECoG fields has increased tenfold in the past decade. These proceedings attempt to summarize the state of the art.

VL - 41 UR - http://www.ncbi.nlm.nih.gov/pubmed/25461213 ER - TY - JOUR T1 - Real-time functional mapping: potential tool for improving language outcome in pediatric epilepsy surgery. JF - J Neurosurg Pediatr Y1 - 2014 A1 - Korostenskaja, Milena A1 - Chen, Po-Ching A1 - Salinas, Christine M A1 - Westerveld, Michael A1 - Peter Brunner A1 - Gerwin Schalk A1 - Cook, Jane C A1 - Baumgartner, James A1 - Lee, Ki H KW - Adolescent KW - Anticonvulsants KW - Brain Mapping KW - Cerebral Cortex KW - Electric Stimulation KW - Electroencephalography KW - Epilepsies, Partial KW - Female KW - Humans KW - Language KW - Neuropsychological Tests KW - Sensitivity and Specificity KW - Speech AB -

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

VL - 14 UR - http://www.ncbi.nlm.nih.gov/pubmed/24995815 IS - 3 ER - TY - JOUR T1 - Real-Time Functional Mapping with Electrocorticography in Pediatric Epilepsy: Comparison with fMRI and ESM Findings. JF - Clinical EEG and neuroscience Y1 - 2014 A1 - Korostenskaja, Milena A1 - Adam J Wilson A1 - Rose, Douglas F A1 - Peter Brunner A1 - Gerwin Schalk A1 - Leach, James A1 - Mangano, Francesco T A1 - Fujiwara, Hisako A1 - Rozhkov, Leonid A1 - Harris, Elana A1 - Chen, Po-Ching A1 - Seo, Joo-Hee A1 - Lee, Ki H KW - Brain-computer interface (BCI) KW - cortical stimulation KW - electrocorticography (ECoG) KW - epilepsy surgery KW - functional magnetic resonance imaging (fMRI) KW - functional mapping KW - pediatrics KW - SIGFRIED AB - SIGFRIED (SIGnal modeling For Real-time Identification and Event Detection) software provides real-time functional mapping (RTFM) of eloquent cortex for epilepsy patients preparing to undergo resective surgery. This study presents the first application of paradigms used in functional magnetic resonance (fMRI) and electrical cortical stimulation mapping (ESM) studies for shared functional cortical mapping in the context of RTFM. Results from the 3 modalities are compared. A left-handed 13-year-old male with intractable epilepsy participated in functional mapping for localization of eloquent language cortex with fMRI, ESM, and RTFM. For RTFM, data were acquired over the frontal and temporal cortex. Several paradigms were sequentially presented: passive (listening to stories) and active (picture naming and verb generation). For verb generation and story processing, fMRI showed atypical right lateralizing language activation within temporal lobe regions of interest and bilateral frontal activation with slight right lateralization. Left hemisphere ESM demonstrated no eloquent language areas. RTFM procedures using story processing and picture naming elicited activity in the right lateral and basal temporal regions. Verb generation elicited strong right lateral temporal lobe activation, as well as left frontal lobe activation. RTFM results confirmed atypical language lateralization evident from fMRI and ESM. We demonstrated the feasibility and usefulness of a new RTFM stimulation paradigm during presurgical evaluation. Block design paradigms used in fMRI may be optimal for this purpose. Further development is needed to create age-appropriate RTFM test batteries. UR - http://www.ncbi.nlm.nih.gov/pubmed/24293161 ER - TY - JOUR T1 - Simultaneous Real-Time Monitoring of Multiple Cortical Systems. JF - Journal of Neural Engineering Y1 - 2014 A1 - Disha Gupta A1 - Jeremy Jeremy Hill A1 - Peter Brunner A1 - Gunduz, Aysegul A1 - A L Ritaccio A1 - Gerwin Schalk KW - auditory processing KW - Electrocorticography KW - movement intention KW - realtime decoding KW - simultaneous decoding AB - OBJECTIVE: Real-time monitoring of the brain is potentially valuable for performance monitoring, communication, training or rehabilitation. In natural situations, the brain performs a complex mix of various sensory, motor or cognitive functions. Thus, real-time brain monitoring would be most valuable if (a) it could decode information from multiple brain systems simultaneously, and (b) this decoding of each brain system were robust to variations in the activity of other (unrelated) brain systems. Previous studies showed that it is possible to decode some information from different brain systems in retrospect and/or in isolation. In our study, we set out to determine whether it is possible to simultaneously decode important information about a user from different brain systems in real time, and to evaluate the impact of concurrent activity in different brain systems on decoding performance. APPROACH: We study these questions using electrocorticographic signals recorded in humans. We first document procedures for generating stable decoding models given little training data, and then report their use for offline and for real-time decoding from 12 subjects (six for offline parameter optimization, six for online experimentation). The subjects engage in tasks that involve movement intention, movement execution and auditory functions, separately, and then simultaneously. Main Results: Our real-time results demonstrate that our system can identify intention and movement periods in single trials with an accuracy of 80.4% and 86.8%, respectively (where 50% would be expected by chance). Simultaneously, the decoding of the power envelope of an auditory stimulus resulted in an average correlation coefficient of 0.37 between the actual and decoded power envelopes. These decoders were trained separately and executed simultaneously in real time. SIGNIFICANCE: This study yielded the first demonstration that it is possible to decode simultaneously the functional activity of multiple independent brain systems. Our comparison of univariate and multivariate decoding strategies, and our analysis of the influence of their decoding parameters, provides benchmarks and guidelines for future research on this topic. UR - http://www.ncbi.nlm.nih.gov/pubmed/25080161 ER - TY - JOUR T1 - Spatial and temporal relationships of electrocorticographic alpha and gamma activity during auditory processing. JF - NeuroImage Y1 - 2014 A1 - Potes, Cristhian A1 - Peter Brunner A1 - Gunduz, Aysegul A1 - Robert T. Knight A1 - Gerwin Schalk KW - alpha and high gamma activity KW - auditory processing KW - electrocorticography (ECoG) KW - functional connectivity KW - granger causality KW - thalamo-cortical interactions AB - Neuroimaging approaches have implicated multiple brain sites in musical perception, including the posterior part of the superior temporal gyrus and adjacent perisylvian areas. However, the detailed spatial and temporal relationship of neural signals that support auditory processing is largely unknown. In this study, we applied a novel inter-subject analysis approach to electrophysiological signals recorded from the surface of the brain (electrocorticography (ECoG)) in ten human subjects. This approach allowed us to reliably identify those ECoG features that were related to the processing of a complex auditory stimulus (i.e., continuous piece of music) and to investigate their spatial, temporal, and causal relationships. Our results identified stimulus-related modulations in the alpha (8-12 Hz) and high gamma (70-110 Hz) bands at neuroanatomical locations implicated in auditory processing. Specifically, we identified stimulus-related ECoG modulations in the alpha band in areas adjacent to primary auditory cortex, which are known to receive afferent auditory projections from the thalamus (80 of a total of 15,107 tested sites). In contrast, we identified stimulus-related ECoG modulations in the high gamma band not only in areas close to primary auditory cortex but also in other perisylvian areas known to be involved in higher-order auditory processing, and in superior premotor cortex (412/15,107 sites). Across all implicated areas, modulations in the high gamma band preceded those in the alpha band by 280 ms, and activity in the high gamma band causally predicted alpha activity, but not vice versa (Granger causality, p<1e(-8)). Additionally, detailed analyses using Granger causality identified causal relationships of high gamma activity between distinct locations in early auditory pathways within superior temporal gyrus (STG) and posterior STG, between posterior STG and inferior frontal cortex, and between STG and premotor cortex. Evidence suggests that these relationships reflect direct cortico-cortical connections rather than common driving input from subcortical structures such as the thalamus. In summary, our inter-subject analyses defined the spatial and temporal relationships between music-related brain activity in the alpha and high gamma bands. They provide experimental evidence supporting current theories about the putative mechanisms of alpha and gamma activity, i.e., reflections of thalamo-cortical interactions and local cortical neural activity, respectively, and the results are also in agreement with existing functional models of auditory processing. VL - 97 UR - http://www.ncbi.nlm.nih.gov/pubmed/24768933 ER - TY - JOUR T1 - Proceedings of the Fourth International Workshop on Advances in Electrocorticography. JF - Epilepsy & Behavior Y1 - 2013 A1 - A L Ritaccio A1 - Peter Brunner A1 - Nathan E. Crone A1 - Gunduz, Aysegul A1 - Hirsch, Lawrence J. A1 - Kanwisher, Nancy A1 - Litt, Brian A1 - Kai J. Miller A1 - Morani, Daniel A1 - Parvizi, Josef A1 - Ramsey, Nick F A1 - Richner, Thomas J. A1 - Tandon, Niton A1 - Williams, Justin A1 - Gerwin Schalk KW - Brain Mapping KW - Brain–computer interface KW - Electrocorticography KW - Gamma-frequency electroencephalography KW - High-frequency oscillations KW - Neuroprosthetics KW - Seizure detection KW - Subdural grid AB - The Fourth International Workshop on Advances in Electrocorticography (ECoG) convened in New Orleans, LA, on October 11–12, 2012. The proceedings of the workshop serves as an accurate record of the most contemporary clinical and experimental work on brain surface recording and represents the insights of a unique multidisciplinary ensemble of expert clinicians and scientists. Presentations covered a broad range of topics, including innovations in passive functional mapping, increased understanding of pathologic high-frequency oscillations, evolving sensor technologies, a human trial of ECoG-driven brain–machine interface, as well as fresh insights into brain electrical stimulation. VL - 29 UR - http://www.ncbi.nlm.nih.gov/pubmed/24034899 IS - 2 ER - TY - JOUR T1 - Toward Gaze-Independent Brain-Computer Interfaces. JF - Clinical Neurophysiology Y1 - 2013 A1 - Peter Brunner A1 - Gerwin Schalk VL - 125 UR - http://www.ncbi.nlm.nih.gov/pubmed/23465431 IS - 5 ER - TY - JOUR T1 - The Tracking of Speech Envelope in the Human Cortex. JF - PLoS ONE Y1 - 2013 A1 - Kubanek, Jan A1 - Peter Brunner A1 - Gunduz, Aysegul A1 - Poeppel, David A1 - Gerwin Schalk AB - Humans are highly adept at processing speech. Recently, it has been shown that slow temporal information in speech (i.e., the envelope of speech) is critical for speech comprehension. Furthermore, it has been found that evoked electric potentials in human cortex are correlated with the speech envelope. However, it has been unclear whether this essential linguistic feature is encoded differentially in specific regions, or whether it is represented throughout the auditory system. To answer this question, we recorded neural data with high temporal resolution directly from the cortex while human subjects listened to a spoken story. We found that the gamma activity in human auditory cortex robustly tracks the speech envelope. The effect is so marked that it is observed during a single presentation of the spoken story to each subject. The effect is stronger in regions situated relatively early in the auditory pathway (belt areas) compared to other regions involved in speech processing, including the superior temporal gyrus (STG) and the posterior inferior frontal gyrus (Broca's region). To further distinguish whether speech envelope is encoded in the auditory system as a phonological (speech-related), or instead as a more general acoustic feature, we also probed the auditory system with a melodic stimulus. We found that belt areas track melody envelope weakly, and as the only region considered. Together, our data provide the first direct electrophysiological evidence that the envelope of speech is robustly tracked in non-primary auditory cortex (belt areas in particular), and suggest that the considered higher-order regions (STG and Broca's region) partake in a more abstract linguistic analysis. VL - 8 UR - http://dx.doi.org/10.1371%2Fjournal.pone.0053398 IS - 1 ER - TY - JOUR T1 - Decoding covert spatial attention using electrocorticographic (ECoG) signals in humans. JF - Neuroimage Y1 - 2012 A1 - Gunduz, Aysegul A1 - Peter Brunner A1 - Amy Daitch A1 - Leuthardt, E C A1 - A L Ritaccio A1 - Pesaran, Bijan A1 - Gerwin Schalk KW - covert attention KW - electrocorticography (ECoG) KW - visual spatial attention AB -

This study shows that electrocorticographic (ECoG) signals recorded from the surface of the brain provide detailed information about shifting of visual attention and its directional orientation in humans. ECoG allows for the identification of the cortical areas and time periods that hold the most information about covert attentional shifts. Our results suggest a transient distributed fronto-parietal mechanism for orienting of attention that is represented by different physiological processes. This neural mechanism encodes not only whether or not a subject shifts their attention to a location, but also the locus of attention. This work contributes to our understanding of the electrophysiological representation of attention in humans. It may also eventually lead to brain-computer interfaces (BCIs) that optimize user interaction with their surroundings or that allow people to communicate choices simply by shifting attention to them.

VL - 60 UR - http://www.ncbi.nlm.nih.gov/pubmed/22366333 IS - 4 ER - TY - JOUR T1 - Decoding Onset and Direction of Movements using Electrocorticographic (ECoG) Signals in Humans. JF - Frontiers in Neuroengineering Y1 - 2012 A1 - Wang, Z. A1 - Gunduz, Aysegul A1 - Peter Brunner A1 - A L Ritaccio A1 - Ji, Q A1 - Gerwin Schalk KW - brain computer interface KW - ECoG KW - movement direction prediction KW - movement onset prediction KW - neurorehabilitation KW - performance augmentation AB - Communication of intent usually requires motor function. This requirement can be limiting when a person is engaged in a task, or prohibitive for some people suffering from neuromuscular disorders. Determining a person's intent, e.g., where and when to move, from brain signals rather than from muscles would have important applications in clinical or other domains. For example, detection of the onset and direction of intended movements may provide the basis for restoration of simple grasping function in people with chronic stroke, or could be used to optimize a user's interaction with the surrounding environment. Detecting the onset and direction of actual movements are a first step in this direction. In this study, we demonstrate that we can detect the onset of intended movements and their direction using electrocorticographic (ECoG) signals recorded from the surface of the cortex in humans. We also demonstrate in a simulation that the information encoded in ECoG about these movements may improve performance in a targeting task. In summary, the results in this paper suggest that detection of intended movement is possible, and may serve useful functions. VL - 5 UR - http://www.ncbi.nlm.nih.gov/pubmed/22891058 IS - 15 ER - TY - JOUR T1 - Dynamics of electrocorticographic (ECoG) activity in human temporal and frontal cortical areas during music listening. JF - Neuroimage Y1 - 2012 A1 - Potes, Cristhian A1 - Gunduz, Aysegul A1 - Peter Brunner A1 - Gerwin Schalk KW - auditory processing KW - electrocorticography (ECoG) KW - high gamma activity KW - sound intensity AB -

Previous studies demonstrated that brain signals encode information about specific features of simple auditory stimuli or of general aspects of natural auditory stimuli. How brain signals represent the time course of specific features in natural auditory stimuli is not well understood. In this study, we show in eight human subjects that signals recorded from the surface of the brain (electrocorticography (ECoG)) encode information about the sound intensity of music. ECoG activity in the high gamma band recorded from the posterior part of the superior temporal gyrus as well as from an isolated area in the precentral gyrus was observed to be highly correlated with the sound intensity of music. These results not only confirm the role of auditory cortices in auditory processing but also point to an important role of premotor and motor cortices. They also encourage the use of ECoG activity to study more complex acoustic features of simple or natural auditory stimuli.

VL - 61 UR - http://www.ncbi.nlm.nih.gov/pubmed/22537600 IS - 4 ER - TY - JOUR T1 - Proceedings of the Third International Workshop on Advances in Electrocorticography. JF - Epilepsy Behav Y1 - 2012 A1 - A L Ritaccio A1 - Beauchamp, Michael A1 - Bosman, Conrado A1 - Peter Brunner A1 - Chang, Edward A1 - Nathan E. Crone A1 - Gunduz, Aysegul A1 - Disha Gupta A1 - Robert T. Knight A1 - Leuthardt, Eric A1 - Litt, Brian A1 - Moran, Daniel A1 - Ojemann, Jeffrey A1 - Parvizi, Josef A1 - Ramsey, Nick A1 - Rieger, Jochem A1 - Viventi, Jonathan A1 - Voytek, Bradley A1 - Williams, Justin A1 - Gerwin Schalk KW - Brain Mapping KW - brain-computer interface KW - Electrocorticography KW - Gamma-frequency electroencephalography KW - high-frequency oscillation KW - Neuroprosthetics KW - Seizure detection KW - Subdural grid AB - The Third International Workshop on Advances in Electrocorticography (ECoG) was convened in Washington, DC, on November 10-11, 2011. As in prior meetings, a true multidisciplinary fusion of clinicians, scientists, and engineers from many disciplines gathered to summarize contemporary experiences in brain surface recordings. The proceedings of this meeting serve as evidence of a very robust and transformative field but will yet again require revision to incorporate the advances that the following year will surely bring. VL - 25 UR - http://www.ncbi.nlm.nih.gov/pubmed/23160096 IS - 4 ER - TY - JOUR T1 - Recording Human Electrocorticographic (ECoG) Signals for Neuroscientific Research and Real-time Functional Cortical Mapping. JF - J Vis Exp Y1 - 2012 A1 - Jeremy Jeremy Hill A1 - Disha Gupta A1 - Peter Brunner A1 - Gunduz, Aysegul A1 - Adamo, Matthew A A1 - A L Ritaccio A1 - Gerwin Schalk KW - BCI2000 KW - brain-computer interfacing KW - Electrocorticography KW - epilepsy monitoring KW - functional brain mapping KW - issue 64 KW - Magnetic Resonance Imaging KW - MRI KW - neuroscience KW - SIGFRIED AB -

Neuroimaging studies of human cognitive, sensory, and motor processes are usually based on noninvasive techniques such as electroencephalography (EEG), magnetoencephalography or functional magnetic-resonance imaging. These techniques have either inherently low temporal or low spatial resolution, and suffer from low signal-to-noise ratio and/or poor high-frequency sensitivity. Thus, they are suboptimal for exploring the short-lived spatio-temporal dynamics of many of the underlying brain processes. In contrast, the invasive technique of electrocorticography (ECoG) provides brain signals that have an exceptionally high signal-to-noise ratio, less susceptibility to artifacts than EEG, and a high spatial and temporal resolution (i.e., <1 cm/<1 millisecond, respectively). ECoG involves measurement of electrical brain signals using electrodes that are implanted subdurally on the surface of the brain. Recent studies have shown that ECoG amplitudes in certain frequency bands carry substantial information about task-related activity, such as motor execution and planning, auditory processing and visual-spatial attention. Most of this information is captured in the high gamma range (around 70-110 Hz). Thus, gamma activity has been proposed as a robust and general indicator of local cortical function. ECoG can also reveal functional connectivity and resolve finer task-related spatial-temporal dynamics, thereby advancing our understanding of large-scale cortical processes. It has especially proven useful for advancing brain-computer interfacing (BCI) technology for decoding a user's intentions to enhance or improve communication and control. Nevertheless, human ECoG data are often hard to obtain because of the risks and limitations of the invasive procedures involved, and the need to record within the constraints of clinical settings. Still, clinical monitoring to localize epileptic foci offers a unique and valuable opportunity to collect human ECoG data. We describe our methods for collecting recording ECoG, and demonstrate how to use these signals for important real-time applications such as clinical mapping and brain-computer interfacing. Our example uses the BCI2000 software platform and the SIGFRIED method, an application for real-time mapping of brain functions. This procedure yields information that clinicians can subsequently use to guide the complex and laborious process of functional mapping by electrical stimulation. PREREQUISITES AND PLANNING: Patients with drug-resistant partial epilepsy may be candidates for resective surgery of an epileptic focus to minimize the frequency of seizures. Prior to resection, the patients undergo monitoring using subdural electrodes for two purposes: first, to localize the epileptic focus, and second, to identify nearby critical brain areas (i.e., eloquent cortex) where resection could result in long-term functional deficits. To implant electrodes, a craniotomy is performed to open the skull. Then, electrode grids and/or strips are placed on the cortex, usually beneath the dura. A typical grid has a set of 8 x 8 platinum-iridium electrodes of 4 mm diameter (2.3 mm exposed surface) embedded in silicon with an inter-electrode distance of 1cm. A strip typically contains 4 or 6 such electrodes in a single line. The locations for these grids/strips are planned by a team of neurologists and neurosurgeons, and are based on previous EEG monitoring, on a structural MRI of the patient's brain, and on relevant factors of the patient's history. Continuous recording over a period of 5-12 days serves to localize epileptic foci, and electrical stimulation via the implanted electrodes allows clinicians to map eloquent cortex. At the end of the monitoring period, explantation of the electrodes and therapeutic resection are performed together in one procedure. In addition to its primary clinical purpose, invasive monitoring also provides a unique opportunity to acquire human ECoG data for neuroscientific research. The decision to include a prospective patient in the research is based on the planned location of their electrodes, on the patient's performance scores on neuropsychological assessments, and on their informed consent, which is predicated on their understanding that participation in research is optional and is not related to their treatment. As with all research involving human subjects, the research protocol must be approved by the hospital's institutional review board. The decision to perform individual experimental tasks is made day-by-day, and is contingent on the patient's endurance and willingness to participate. Some or all of the experiments may be prevented by problems with the clinical state of the patient, such as post-operative facial swelling, temporary aphasia, frequent seizures, post-ictal fatigue and confusion, and more general pain or discomfort. At the Epilepsy Monitoring Unit at Albany Medical Center in Albany, New York, clinical monitoring is implemented around the clock using a 192-channel Nihon-Kohden Neurofax monitoring system. Research recordings are made in collaboration with the Wadsworth Center of the New York State Department of Health in Albany. Signals from the ECoG electrodes are fed simultaneously to the research and the clinical systems via splitter connectors. To ensure that the clinical and research systems do not interfere with each other, the two systems typically use separate grounds. In fact, an epidural strip of electrodes is sometimes implanted to provide a ground for the clinical system. Whether research or clinical recording system, the grounding electrode is chosen to be distant from the predicted epileptic focus and from cortical areas of interest for the research. Our research system consists of eight synchronized 16-channel g.USBamp amplifier/digitizer units (g.tec, Graz, Austria). These were chosen because they are safety-rated and FDA-approved for invasive recordings, they have a very low noise-floor in the high-frequency range in which the signals of interest are found, and they come with an SDK that allows them to be integrated with custom-written research software. In order to capture the high-gamma signal accurately, we acquire signals at 1200Hz sampling rate-considerably higher than that of the typical EEG experiment or that of many clinical monitoring systems. A built-in low-pass filter automatically prevents aliasing of signals higher than the digitizer can capture. The patient's eye gaze is tracked using a monitor with a built-in Tobii T-60 eye-tracking system (Tobii Tech., Stockholm, Sweden). Additional accessories such as joystick, bluetooth Wiimote (Nintendo Co.), data-glove (5(th) Dimension Technologies), keyboard, microphone, headphones, or video camera are connected depending on the requirements of the particular experiment. Data collection, stimulus presentation, synchronization with the different input/output accessories, and real-time analysis and visualization are accomplished using our BCI2000 software. BCI2000 is a freely available general-purpose software system for real-time biosignal data acquisition, processing and feedback. It includes an array of pre-built modules that can be flexibly configured for many different purposes, and that can be extended by researchers' own code in C++, MATLAB or Python. BCI2000 consists of four modules that communicate with each other via a network-capable protocol: a Source module that handles the acquisition of brain signals from one of 19 different hardware systems from different manufacturers; a Signal Processing module that extracts relevant ECoG features and translates them into output signals; an Application module that delivers stimuli and feedback to the subject; and the Operator module that provides a graphical interface to the investigator. A number of different experiments may be conducted with any given patient. The priority of experiments will be determined by the location of the particular patient's electrodes. However, we usually begin our experimentation using the SIGFRIED (SIGnal modeling For Realtime Identification and Event Detection) mapping method, which detects and displays significant task-related activity in real time. The resulting functional map allows us to further tailor subsequent experimental protocols and may also prove as a useful starting point for traditional mapping by electrocortical stimulation (ECS). Although ECS mapping remains the gold standard for predicting the clinical outcome of resection, the process of ECS mapping is time consuming and also has other problems, such as after-discharges or seizures. Thus, a passive functional mapping technique may prove valuable in providing an initial estimate of the locus of eloquent cortex, which may then be confirmed and refined by ECS. The results from our passive SIGFRIED mapping technique have been shown to exhibit substantial concurrence with the results derived using ECS mapping. The protocol described in this paper establishes a general methodology for gathering human ECoG data, before proceeding to illustrate how experiments can be initiated using the BCI2000 software platform. Finally, as a specific example, we describe how to perform passive functional mapping using the BCI2000-based SIGFRIED system.

UR - http://www.ncbi.nlm.nih.gov/pubmed/22782131 IS - 64 ER - TY - JOUR T1 - Current Trends in Hardware and Software for Brain-Computer Interfaces (BCIs). JF - J Neural Eng Y1 - 2011 A1 - Peter Brunner A1 - Bianchi, L A1 - Guger, C A1 - Cincotti, F A1 - Gerwin Schalk KW - Biofeedback, Psychology KW - Brain KW - Brain Mapping KW - Electroencephalography KW - Equipment Design KW - Equipment Failure Analysis KW - Humans KW - Man-Machine Systems KW - Software KW - User-Computer Interface AB -

brain-computer interface (BCI) provides a non-muscular communication channel to people with and without disabilities. BCI devices consist of hardware and software. BCI hardware records signals from the brain, either invasively or non-invasively, using a series of device components. BCI software then translates these signals into device output commands and provides feedback. One may categorize different types of BCI applications into the following four categories: basic research, clinical/translational research, consumer products, and emerging applications. These four categories use BCI hardware and software, but have different sets of requirements. For example, while basic research needs to explore a wide range of system configurations, and thus requires a wide range of hardware and software capabilities, applications in the other three categories may be designed for relatively narrow purposes and thus may only need a very limited subset of capabilities. This paper summarizes technical aspects for each of these four categories of BCI applications. The results indicate that BCI technology is in transition from isolated demonstrations to systematic research and commercial development. This process requires several multidisciplinary efforts, including the development of better integrated and more robust BCI hardware and software, the definition of standardized interfaces, and the developmentof certification, dissemination and reimbursement procedures.

VL - 8 UR - http://www.ncbi.nlm.nih.gov/pubmed/21436536 IS - 2 ER - TY - JOUR T1 - Neural Correlates of Covert Attention in Electrocorticographic (ECoG) Signals in Humans. JF - Front Hum Neurosci Y1 - 2011 A1 - Gunduz, Aysegul A1 - Peter Brunner A1 - Amy Daitch A1 - Leuthardt, E C A1 - A L Ritaccio A1 - Pesaran, Bijan A1 - Gerwin Schalk KW - covert attention KW - Electrocorticography KW - intention KW - motor response KW - visual-spatial attention AB -

Attention is a cognitive selection mechanism that allocates the limited processing resources of the brain to the sensory streams most relevant to our immediate goals, thereby enhancing responsiveness and behavioral performance. The underlying neural mechanisms of orienting attention are distributed across a widespread cortical network. While aspects of this network have been extensively studied, details about the electrophysiological dynamics of this network are scarce. In this study, we investigated attentional networks using electrocorticographic (ECoG) recordings from the surface of the brain, which combine broad spatial coverage with high temporal resolution, in five human subjects. ECoG was recorded when subjects covertly attended to a spatial location and responded to contrast changes in the presence of distractors in a modified Posner cueing task. ECoG amplitudes in the alpha, beta, and gamma bands identified neural changes associated with covert attention and motor preparation/execution in the different stages of the task. The results show that attentional engagement was primarily associated with ECoG activity in the visual, prefrontal, premotor, and parietal cortices. Motor preparation/execution was associated with ECoG activity in premotor/sensorimotor cortices. In summary, our results illustrate rich and distributed cortical dynamics that are associated with orienting attention and the subsequent motor preparation and execution. These findings are largely consistent with and expand on primate studies using intracortical recordings and human functional neuroimaging studies.

VL - 5 UR - http://www.ncbi.nlm.nih.gov/pubmed/22046153 ER - TY - JOUR T1 - Proceedings of the Second International Workshop on Advances in Electrocorticography. JF - Epilepsy Behav Y1 - 2011 A1 - A L Ritaccio A1 - Boatman-Reich, Dana A1 - Peter Brunner A1 - Cervenka, Mackenzie C A1 - Cole, Andrew J A1 - Nathan E. Crone A1 - Duckrow, Robert A1 - Korzeniewska, Anna A1 - Litt, Brian A1 - Miller, John W A1 - Moran, D A1 - Parvizi, Josef A1 - Viventi, Jonathan A1 - Williams, Justin C A1 - Gerwin Schalk KW - Brain KW - Brain Mapping KW - Brain Waves KW - Diagnosis, Computer-Assisted KW - Electroencephalography KW - Epilepsy KW - Humans KW - United States KW - User-Computer Interface AB -

The Second International Workshop on Advances in Electrocorticography (ECoG) was convened in San Diego, CA, USA, on November 11-12, 2010. Between this meeting and the inaugural 2009 event, a much clearer picture has been emerging of cortical ECoG physiology and its relationship to local field potentials and single-cell recordings. Innovations in material engineering are advancing the goal of a stable long-term recording interface. Continued evolution of ECoG-driven brain-computer interface technology is determining innovation in neuroprosthetics. Improvements in instrumentation and statistical methodologies continue to elucidate ECoG correlates of normal human function as well as the ictal state. This proceedings document summarizes the current status of this rapidly evolving field.

VL - 22 UR - http://www.ncbi.nlm.nih.gov/pubmed/22036287 IS - 4 ER - TY - JOUR T1 - Rapid Communication with a "P300" Matrix Speller Using Electrocorticographic Signals (ECoG). JF - Front Neurosci Y1 - 2011 A1 - Peter Brunner A1 - A L Ritaccio A1 - Emrich, Joseph F A1 - H Bischof A1 - Gerwin Schalk KW - brain-computer interface KW - Electrocorticography KW - event-related potential KW - P300 KW - speller AB -

brain-computer interface (BCI) can provide a non-muscular communication channel to severely disabled people. One particular realization of a BCI is the P300 matrix speller that was originally described by Farwell and Donchin (1988). This speller uses event-related potentials (ERPs) that include the P300 ERP. All previous online studies of the P300 matrix speller used scalp-recorded electroencephalography (EEG) and were limited in their communication performance to only a few characters per minute. In our study, we investigated the feasibility of using electrocorticographic (ECoG) signals for online operation of the matrix speller, and determined associated spelling rates. We used the matrix speller that is implemented in the BCI2000 system. This speller used ECoG signals that were recorded from frontal, parietal, and occipital areas in one subject. This subject spelled a total of 444 characters in online experiments. The results showed that the subject sustained a rate of 17 characters/min (i.e., 69 bits/min), and achieved a peak rate of 22 characters/min (i.e., 113 bits/min). Detailed analysis of the results suggests that ERPs over visual areas (i.e., visual evoked potentials) contribute significantly to the performance of the matrix speller BCI system. Our results also point to potential reasons for the apparent advantages in spelling performance of ECoG compared to EEG. Thus, with additional verification in more subjects, these results may further extend the communication options for people with serious neuromuscular disabilities.

VL - 5 UR - http://www.ncbi.nlm.nih.gov/pubmed/21369351 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 - Toward a gaze-independent matrix speller brain-computer interface. JF - Clin Neurophysiol Y1 - 2011 A1 - Peter Brunner A1 - Gerwin Schalk KW - Attention KW - Brain KW - Fixation, Ocular KW - Humans KW - User-Computer Interface VL - 122 UR - http://www.ncbi.nlm.nih.gov/pubmed/21183404 IS - 6 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 - Passive real-time identification of speech and motor cortex during an awake craniotomy. JF - Epilepsy Behav Y1 - 2010 A1 - Roland, Jarod A1 - Peter Brunner A1 - Johnston, James A1 - Gerwin Schalk A1 - Leuthardt, E C KW - Brain Mapping KW - Brain Neoplasms KW - Cerebral Cortex KW - Craniotomy KW - Electric Stimulation KW - Electroencephalography KW - Humans KW - Neurologic Examination AB -

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

VL - 18 UR - http://www.ncbi.nlm.nih.gov/pubmed/20478745 IS - 1-2 ER - TY - JOUR T1 - Proceedings of the first international workshop on advances in electrocorticography. JF - Epilepsy Behav Y1 - 2010 A1 - A L Ritaccio A1 - Peter Brunner A1 - Cervenka, Mackenzie C A1 - Nathan E. Crone A1 - Guger, C A1 - Leuthardt, E C A1 - Oostenveld, Robert A1 - Stacey, William A1 - Gerwin Schalk KW - Brain KW - Brain Mapping KW - Diagnosis, Computer-Assisted KW - Electroencephalography KW - Humans KW - International Cooperation KW - Seizures KW - Signal Detection, Psychological AB -

In October 2009, a group of neurologists, neurosurgeons, computational neuroscientists, and engineers congregated to present novel developments transforming human electrocorticography (ECoG) beyond its established relevance in clinical epileptology. The contents of the proceedings advanced the role of ECoG in seizure detection and prediction, neurobehavioral research, functional mapping, and brain-computer interface technology. The meeting established the foundation for future work on the methodology and application of surface brain recordings.

VL - 19 UR - http://www.ncbi.nlm.nih.gov/pubmed/20889384 IS - 3 ER - TY - CONF T1 - Brain-Computer Interaction. T2 - 5th Intl. Conference on Augmented Cognition Y1 - 2009 A1 - Peter Brunner A1 - Gerwin Schalk KW - BCI KW - brain-computer interface KW - neural engineering KW - neural prosthesis AB -

Detection and automated interpretation of attention-related or intention-related brain activity carries significant promise for many military and civilian applications. This interpretation of brain activity could provide information about a person’s intended movements, imagined movements, or attentional focus, and thus could be valuable for optimizing or replacing traditional motor-based communication between a person and a computer or other output devices. We describe here the objective and preliminary results of our studies in this area.

JF - 5th Intl. Conference on Augmented Cognition PB - Springer SN - 978-3-642-02811-3 UR - http://link.springer.com/chapter/10.1007%2F978-3-642-02812-0_81 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 - A scanning protocol for a sensorimotor rhythm-based brain-computer interface. JF - Biological psychology Y1 - 2009 A1 - Friedrich, Elisabeth V. C. A1 - Dennis J. McFarland A1 - Neuper, Christa A1 - Theresa M Vaughan A1 - Peter Brunner A1 - Jonathan Wolpaw KW - BCI KW - brain-computer interface KW - scanning protocol KW - sensorimotor rhythm AB - The scanning protocol is a novel brain-computer interface (BCI) implementation that can be controlled with sensorimotor rhythms (SMRs) of the electroencephalogram (EEG). The user views a screen that shows four choices in a linear array with one marked as target. The four choices are successively highlighted for 2.5s each. When a target is highlighted, the user can select it by modulating the SMR. An advantage of this method is the capacity to choose among multiple choices with just one learned SMR modulation. Each of 10 naive users trained for ten 30 min sessions over 5 weeks. User performance improved significantly (p<0.001) over the sessions and ranged from 30 to 80% mean accuracy of the last three sessions (chance accuracy=25%). The incidence of correct selections depended on the target position. These results suggest that, with further improvements, a scanning protocol can be effective. The ultimate goal is to expand it to a large matrix of selections. VL - 80 UR - http://www.ncbi.nlm.nih.gov/pubmed/18786603 ER - TY - JOUR T1 - Toward a high-throughput auditory P300-based brain-computer interface. JF - Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology Y1 - 2009 A1 - Klobassa, D. S. A1 - Theresa M Vaughan A1 - Peter Brunner A1 - Schwartz, N. E. A1 - Jonathan Wolpaw A1 - Neuper, C. A1 - Sellers, E. W. KW - brain-computer interface KW - brain-machine interface KW - EEG KW - event-related potential KW - P300 KW - Rehabilitation AB - OBJECTIVE: Brain-computer interface (BCI) technology can provide severely disabled people with non-muscular communication. For those most severely disabled, limitations in eye mobility or visual acuity may necessitate auditory BCI systems. The present study investigates the efficacy of the use of six environmental sounds to operate a 6x6 P300 Speller. METHODS: A two-group design was used to ascertain whether participants benefited from visual cues early in training. Group A (N=5) received only auditory stimuli during all 11 sessions, whereas Group AV (N=5) received simultaneous auditory and visual stimuli in initial sessions after which the visual stimuli were systematically removed. Stepwise linear discriminant analysis determined the matrix item that elicited the largest P300 response and thereby identified the desired choice. RESULTS: Online results and offline analyses showed that the two groups achieved equivalent accuracy. In the last session, eight of 10 participants achieved 50% or more, and four of these achieved 75% or more, online accuracy (2.8% accuracy expected by chance). Mean bit rates averaged about 2 bits/min, and maximum bit rates reached 5.6 bits/min. CONCLUSIONS: This study indicates that an auditory P300 BCI is feasible, that reasonable classification accuracy and rate of communication are achievable, and that the paradigm should be further evaluated with a group of severely disabled participants who have limited visual mobility. SIGNIFICANCE: With further development, this auditory P300 BCI could be of substantial value to severely disabled people who cannot use a visual BCI. VL - 120 UR - http://www.ncbi.nlm.nih.gov/pubmed/19574091 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 - Interferon-gamma limits the availability of iron for intramacrophage Salmonella typhimurium. JF - Eur J Immunol Y1 - 2008 A1 - Nairz, Manfred A1 - Fritsche, Gernot A1 - Peter Brunner A1 - Talasz, Heribert A1 - Hantke, Klaus A1 - Weiss, Günter KW - Acute-Phase Proteins KW - Animals KW - Antimicrobial Cationic Peptides KW - Cation Transport Proteins KW - Cell Line KW - Ferritins KW - Heme Oxygenase (Decyclizing) KW - Hepcidins KW - Interferon-gamma KW - Iron KW - Lipocalins KW - Macrophages KW - Mice KW - Nitric Oxide KW - Oncogene Proteins KW - Salmonella typhimurium KW - Transferrin KW - Tumor Necrosis Factor-alpha AB -

In stimulating effector functions of mononuclear phagocytes, IFN-gamma is of pivotal importance in host defense against intramacrophage pathogens including salmonellae. As the activity of IFN-gamma is modulated by iron and since a sufficient availability of iron is essential for the growth of pathogens, we investigated the regulatory effects of IFN-gamma on iron homeostasis and immune function in murine macrophages infected with Salmonella typhimurium. In Salmonella-infected phagocytes, IFN-gamma caused a significant reduction of iron uptake via transferrin receptor 1 and resulted in an increased iron efflux caused by an enhanced expression of the iron exporter ferroportin 1. Moreover, the expression of haem oxygenase 1 and of the siderophore-capturing antimicrobial peptide lipocalin 2 was markedly elevated following bacterial invasion, with IFN-gamma exerting a super-inducing effect. This observed regulatory impact of IFN-gamma reduced the intracellular iron pools within infected phagocytes, thus restricting the acquisition of iron by engulfed Salmonella typhimurium while concomitantly promoting NO and TNF-alpha production. Our data suggest that the modulation of crucial pathways of macrophage iron metabolism in response to IFN-gamma concordantly aims at withdrawing iron from intracellular Salmonella and at strengthening macrophage immune response functions. These regulations are thus consistent with the principles of nutritional immunity.

VL - 38 UR - http://www.ncbi.nlm.nih.gov/pubmed/18581323 IS - 7 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 - JOUR T1 - Pathways for the regulation of body iron homeostasis in response to experimental iron overload. JF - J Hepatol Y1 - 2005 A1 - Theurl, Igor A1 - Ludwiczek, Susanne A1 - Eller, Philipp A1 - Seifert, Markus A1 - Artner, Erika A1 - Peter Brunner A1 - Weiss, Günter KW - Animals KW - Disease Models, Animal KW - Disease Progression KW - DNA Primers KW - Duodenum KW - Gene Expression Regulation KW - Hepatocytes KW - Homeostasis KW - Iron KW - Iron Overload KW - Macrophages KW - Mice KW - Mice, Inbred C57BL KW - Polymerase Chain Reaction KW - RNA AB - BACKGROUND/AIMS: Secondary iron overload is a frequent clinical condition found in association with multiple blood transfusions. METHODS: To gain insight into adaptive changes in the expression of iron genes in duodenum, liver and spleen upon experimental iron overload we studied C57BL/6 mice receiving repetitive daily injections of iron-dextran for up to 5 days. RESULTS: Iron initially accumulated in spleen macrophages but with subsequent increase in macrophage ferroportin and ferritin expression its content in the spleen decreased while a progressive storage of iron occurred within hepatocytes which was paralleled by a significant increase in hepcidin and hemojuvelin expression. Under these conditions, iron was still absorbed from the duodenal lumen as divalent metal transporter-1 expressions were high, however, most of the absorbed iron was incorporated into duodenal ferritin, while ferroportin expression drastically decreased and iron transfer to the circulation was reduced. CONCLUSIONS: Experimental iron overload results in iron accumulation in macrophages and later in hepatocytes. In parallel, the transfer of iron from the gut to the circulation is diminished which may be referred to interference of hepcidin with ferroportin mediated iron export, thus preventing body iron accumulation. VL - 43 UR - http://www.sciencedirect.com/science/article/pii/S0168827805003168# IS - 4 ER -