@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 {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} }