@article {3366, title = {Electrocorticographic representations of segmental features in continuous speech.}, journal = {Front Hum Neurosci}, volume = {9}, year = {2015}, month = {02/2015}, pages = {97}, abstract = {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.}, keywords = {electrocorticography (ECoG), manner of articulation, place of articulation, speech processing, voicing}, issn = {1662-5161}, doi = {10.3389/fnhum.2015.00097}, url = {http://www.ncbi.nlm.nih.gov/pubmed/25759647}, author = {Lotte, Fabien and Jonathan S Brumberg and Peter Brunner and Gunduz, Aysegul and A L Ritaccio and Guan, Cuntai and Gerwin Schalk} } @article {3418, title = {Identifying the Attended Speaker Using Electrocorticographic (ECoG) Signals.}, journal = {Journal of Neural Engineering}, year = {2015}, abstract = {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{\textendash}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.}, keywords = {auditory attention, Brain-computer interface (BCI), Cocktail Party, electrocorticography (ECoG)}, doi = {10.1080/2326263X.2015.1063363}, url = {https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4776341/}, author = {Dijkstra, K. and Peter Brunner and Gunduz, Aysegul and Coon, W.G. and A L Ritaccio and Farquhar, Jason and Gerwin Schalk} } @article {3406, title = {ECoG high gamma activity reveals distinct cortical representations of lyrics passages, harmonic and timbre-related changes in a rock song.}, journal = {Front Hum Neurosci}, volume = {8}, year = {2014}, month = {10/2014}, pages = {798}, abstract = {

Listening to music moves our minds and moods, stirring interest in its neural underpinnings. A multitude of compositional features drives the appeal of natural music. How such original music, where a composer{\textquoteright}s opus is not manipulated for experimental purposes, engages a listener{\textquoteright}s brain has not been studied until recently. Here, we report an in-depth analysis of two electrocorticographic (ECoG) data sets obtained over the left hemisphere in ten patients during presentation of either a rock song or a read-out narrative. First, the time courses of five acoustic features (intensity, presence/absence of vocals with lyrics, spectral centroid, harmonic change, and pulse clarity) were extracted from the audio tracks and found to be correlated with each other to varying degrees. In a second step, we uncovered the specific impact of each musical feature on ECoG high-gamma power (70-170 Hz) by calculating partial correlations to remove the influence of the other four features. In the music condition, the onset and offset of vocal lyrics in ongoing instrumental music was consistently identified within the group as the dominant driver for ECoG high-gamma power changes over temporal auditory areas, while concurrently subject-individual activation spots were identified for sound intensity, timbral, and harmonic features. The distinct cortical activations to vocal speech-related content embedded in instrumental music directly demonstrate that song integrated in instrumental music represents a distinct dimension in complex music. In contrast, in the speech condition, the full sound envelope was reflected in the high gamma response rather than the onset or offset of the vocal lyrics. This demonstrates how the contributions of stimulus features that modulate the brain response differ across the two examples of a full-length natural stimulus, which suggests a context-dependent feature selection in the processing of complex auditory stimuli.

}, keywords = {acoustic features, electrocorticography (ECoG), high gamma, music processing, natural music}, issn = {1662-5161}, doi = {10.3389/fnhum.2014.00798}, url = {http://www.ncbi.nlm.nih.gov/pubmed/25352799}, author = {Sturm, Irene and Benjamin Blankertz and Potes, Cristhian and Gerwin Schalk and Curio, Gabriel} } @article {3405, title = {Localizing ECoG electrodes on the cortical anatomy without post-implantation imaging.}, journal = {Neuroimage Clin}, volume = {6}, year = {2014}, month = {08/2014}, pages = {64-76}, abstract = {

INTRODUCTION: Electrocorticographic (ECoG) grids are placed subdurally on the cortex in people undergoing cortical resection to delineate eloquent cortex. ECoG signals have high spatial and temporal resolution and thus can be valuable for neuroscientific research. The value of these data is highest when they can be related to the cortical anatomy. Existing methods that establish this relationship rely either on post-implantation imaging using computed tomography (CT), magnetic resonance imaging (MRI) or X-Rays, or on intra-operative photographs. For research purposes, it is desirable to localize ECoG electrodes on the brain anatomy even when post-operative imaging is not available or when intra-operative photographs do not readily identify anatomical landmarks.

METHODS: We developed a method to co-register ECoG electrodes to the underlying cortical anatomy using only a pre-operative MRI, a clinical neuronavigation device (such as BrainLab VectorVision), and fiducial markers. To validate our technique, we compared our results to data collected from six subjects who also had post-grid implantation imaging available. We compared the electrode coordinates obtained by our fiducial-based method to those obtained using existing methods, which are based on co-registering pre- and post-grid implantation images.

RESULTS: Our fiducial-based method agreed with the MRI-CT method to within an average of 8.24 mm (mean, median = 7.10 mm) across 6 subjects in 3 dimensions. It showed an average discrepancy of 2.7 mm when compared to the results of the intra-operative photograph method in a 2D coordinate system. As this method does not require post-operative imaging such as CTs, our technique should prove useful for research in intra-operative single-stage surgery scenarios. To demonstrate the use of our method, we applied our method during real-time mapping of eloquent cortex during a single-stage surgery. The results demonstrated that our method can be applied intra-operatively in the absence of post-operative imaging to acquire ECoG signals that can be valuable for neuroscientific investigations.

}, keywords = {auditory processing, electrocorticography (ECoG), electrode localization, fiducials, interaoperative localization}, issn = {2213-1582}, doi = {10.1016/j.nicl.2014.07.015}, url = {http://www.ncbi.nlm.nih.gov/pubmed/25379417}, author = {Disha Gupta and Jeremy Jeremy Hill and Adamo, Matthew A and A L Ritaccio and Gerwin Schalk} } @article {3357, title = {Real-Time Functional Mapping with Electrocorticography in Pediatric Epilepsy: Comparison with fMRI and ESM Findings.}, journal = {Clinical EEG and neuroscience}, year = {2014}, month = {07/2014}, abstract = {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.}, keywords = {Brain-computer interface (BCI), cortical stimulation, electrocorticography (ECoG), epilepsy surgery, functional magnetic resonance imaging (fMRI), functional mapping, pediatrics, SIGFRIED}, doi = {10.1177/1550059413492960}, url = {http://www.ncbi.nlm.nih.gov/pubmed/24293161}, author = {Korostenskaja, Milena and Adam J Wilson and Rose, Douglas F and Peter Brunner and Gerwin Schalk and Leach, James and Mangano, Francesco T and Fujiwara, Hisako and Rozhkov, Leonid and Harris, Elana and Chen, Po-Ching and Seo, Joo-Hee and Lee, Ki H} } @article {2950, title = {Spatial and temporal relationships of electrocorticographic alpha and gamma activity during auditory processing.}, journal = {NeuroImage}, volume = {97}, year = {2014}, month = {08/2014}, pages = {188-95}, abstract = {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.}, keywords = {alpha and high gamma activity, auditory processing, electrocorticography (ECoG), functional connectivity, granger causality, thalamo-cortical interactions}, doi = {10.1016/j.neuroimage.2014.04.045}, url = {http://www.ncbi.nlm.nih.gov/pubmed/24768933}, author = {Potes, Cristhian and Peter Brunner and Gunduz, Aysegul and Robert T. Knight and Gerwin Schalk} } @article {2102, title = {Decoding covert spatial attention using electrocorticographic (ECoG) signals in humans.}, journal = {Neuroimage}, volume = {60}, year = {2012}, month = {05/2012}, pages = {2285-93}, abstract = {

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.

}, keywords = {covert attention, electrocorticography (ECoG), visual spatial attention}, issn = {1095-9572}, doi = {10.1016/j.neuroimage.2012.02.017}, url = {http://www.ncbi.nlm.nih.gov/pubmed/22366333}, author = {Gunduz, Aysegul and Peter Brunner and Amy Daitch and Leuthardt, E C and A L Ritaccio and Pesaran, Bijan and Gerwin Schalk} } @article {2103, title = {Dynamics of electrocorticographic (ECoG) activity in human temporal and frontal cortical areas during music listening.}, journal = {Neuroimage}, volume = {61}, year = {2012}, month = {07/2012}, pages = {841-8}, abstract = {

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.

}, keywords = {auditory processing, electrocorticography (ECoG), high gamma activity, sound intensity}, issn = {1095-9572}, doi = {10.1016/j.neuroimage.2012.04.022}, url = {http://www.ncbi.nlm.nih.gov/pubmed/22537600}, author = {Potes, Cristhian and Gunduz, Aysegul and Peter Brunner and Gerwin Schalk} } @article {2209, title = {Brain-computer interfaces using electrocorticographic signals.}, journal = {IEEE Rev Biomed Eng}, volume = {4}, year = {2011}, month = {10/2011}, pages = {140-54}, abstract = {

Many studies over the past two decades have shown that people and animals can use brain signals to convey their intent to a computer using brain-computer interfaces (BCIs). BCI systems measure specific features of brain activity and translate them into control signals that drive an output. The sensor modalities that have most commonly been used in BCI studies have been electroencephalographic (EEG) recordings from the scalp and single-neuron recordings from within the cortex. Over the past decade, an increasing number of studies has explored the use of electrocorticographic (ECoG) activity recorded directly from the surface of the brain. ECoG has attracted substantial and increasing interest, because it has been shown to reflect specific details of actual and imagined actions, and because its technical characteristics should readily support robust and chronic implementations of BCI systems in humans. This review provides general perspectives on the ECoG platform; describes the different electrophysiological features that can be detected in ECoG; elaborates on the signal acquisition issues, protocols, and online performance of ECoG-based BCI studies to date; presents important limitations of current ECoG studies; discusses opportunities for further research; and finally presents a vision for eventual clinical implementation. In summary, the studies presented to date strongly encourage further research using the ECoG platform for basic neuroscientific research, as well as for translational neuroprosthetic applications.

}, keywords = {Brain-computer interface (BCI), brain-machine interface (BMI), electrocorticography (ECoG)}, issn = {1941-1189}, doi = {10.1109/RBME.2011.2172408}, url = {http://www.ncbi.nlm.nih.gov/pubmed/22273796}, author = {Gerwin Schalk and Leuthardt, E C} }