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  1. Article ; Online: Detection of common EEG phenomena using individual electrodes placed outside the hair.

    Schalk, Gerwin / Shao, Shiyun / Xiao, Kewei / Wu, Zehan

    Biomedical physics & engineering express

    2023  Volume 10, Issue 1

    Abstract: Many studies over the past decades have provided exciting evidence that electrical signals recorded from the scalp (electroencephalogram, EEG) hold meaningful information about the brain's function or dysfunction. This information is used routinely in ... ...

    Abstract Many studies over the past decades have provided exciting evidence that electrical signals recorded from the scalp (electroencephalogram, EEG) hold meaningful information about the brain's function or dysfunction. This information is used routinely in research laboratories to test specific hypotheses and in clinical settings to aid in diagnoses (such as during polysomnography evaluations). Unfortunately, with very few exceptions, such meaningful information about brain function has not yet led to valuable solutions that can address the needs of many people outside such research laboratories or clinics. One of the major hurdles to practical application of EEG-based neurotechnologies is the current predominant requirement to use electrodes that are placed in the hair, which greatly reduces practicality and cosmesis. While several studies reported results using one specific combination of signal/reference electrode outside the hair in one specific context (such as a brain-computer interface experiment), it has been unclear what information about brain function can be acquired using different signal/referencing locations placed outside the hair. To address this issue, in this study, we set out to determine to what extent EEG phenomena related to auditory, visual, cognitive, motor, and sleep function can be detected from different combinations of individual signal/referencing electrodes that are placed outside the hair. The results of our study from 15 subjects suggest that only a few EEG electrodes placed in locations on the forehead or around the ear can provide substantial task-related information in 6 of 7 tasks. Thus, the results of our study provide encouraging evidence and guidance that should invigorate and facilitate the translation of laboratory experiments into practical, useful, and valuable EEG-based neurotechnology solutions.
    MeSH term(s) Humans ; Electrodes ; Scalp ; Electroencephalography/methods ; Polysomnography ; Brain-Computer Interfaces
    Language English
    Publishing date 2023-12-14
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ISSN 2057-1976
    ISSN (online) 2057-1976
    DOI 10.1088/2057-1976/ad12f9
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  2. Article: A general framework for dynamic cortical function: the function-through-biased-oscillations (FBO) hypothesis.

    Schalk, Gerwin

    Frontiers in human neuroscience

    2015  Volume 9, Page(s) 352

    Abstract: A central goal of neuroscience is to determine how the brain's relatively static anatomy can support dynamic cortical function, i.e., cortical function that varies according to task demands. In pursuit of this goal, scientists have produced a large ... ...

    Abstract A central goal of neuroscience is to determine how the brain's relatively static anatomy can support dynamic cortical function, i.e., cortical function that varies according to task demands. In pursuit of this goal, scientists have produced a large number of experimental results and established influential conceptual frameworks, in particular communication-through-coherence (CTC) and gating-by-inhibition (GBI), but these data and frameworks have not provided a parsimonious view of the principles that underlie cortical function. Here I synthesize these existing experimental results and the CTC and GBI frameworks, and propose the function-through-biased-oscillations (FBO) hypothesis as a model to understand dynamic cortical function. The FBO hypothesis suggests that oscillatory voltage amplitude is the principal measurement that directly reflects cortical excitability, that asymmetries in voltage amplitude explain a range of brain signal phenomena, and that predictive variations in such asymmetric oscillations provide a simple and general model for information routing that can help to explain dynamic cortical function.
    Language English
    Publishing date 2015-06-16
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2425477-0
    ISSN 1662-5161
    ISSN 1662-5161
    DOI 10.3389/fnhum.2015.00352
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  3. Article ; Online: A neural population selective for song in human auditory cortex.

    Norman-Haignere, Sam V / Feather, Jenelle / Boebinger, Dana / Brunner, Peter / Ritaccio, Anthony / McDermott, Josh H / Schalk, Gerwin / Kanwisher, Nancy

    Current biology : CB

    2022  Volume 32, Issue 6, Page(s) 1454–1455

    Language English
    Publishing date 2022-03-27
    Publishing country England
    Document type Published Erratum
    ZDB-ID 1071731-6
    ISSN 1879-0445 ; 0960-9822
    ISSN (online) 1879-0445
    ISSN 0960-9822
    DOI 10.1016/j.cub.2022.03.016
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  4. Article ; Online: Can Electrocorticography (ECoG) Support Robust and Powerful Brain-Computer Interfaces?

    Schalk, Gerwin

    Frontiers in neuroengineering

    2010  Volume 3, Page(s) 9

    Language English
    Publishing date 2010-06-24
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2452978-3
    ISSN 1662-6443 ; 1662-6443
    ISSN (online) 1662-6443
    ISSN 1662-6443
    DOI 10.3389/fneng.2010.00009
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  5. Article ; Online: Music can be reconstructed from human auditory cortex activity using nonlinear decoding models.

    Bellier, Ludovic / Llorens, Anaïs / Marciano, Déborah / Gunduz, Aysegul / Schalk, Gerwin / Brunner, Peter / Knight, Robert T

    PLoS biology

    2023  Volume 21, Issue 8, Page(s) e3002176

    Abstract: Music is core to human experience, yet the precise neural dynamics underlying music perception remain unknown. We analyzed a unique intracranial electroencephalography (iEEG) dataset of 29 patients who listened to a Pink Floyd song and applied a stimulus ...

    Abstract Music is core to human experience, yet the precise neural dynamics underlying music perception remain unknown. We analyzed a unique intracranial electroencephalography (iEEG) dataset of 29 patients who listened to a Pink Floyd song and applied a stimulus reconstruction approach previously used in the speech domain. We successfully reconstructed a recognizable song from direct neural recordings and quantified the impact of different factors on decoding accuracy. Combining encoding and decoding analyses, we found a right-hemisphere dominance for music perception with a primary role of the superior temporal gyrus (STG), evidenced a new STG subregion tuned to musical rhythm, and defined an anterior-posterior STG organization exhibiting sustained and onset responses to musical elements. Our findings show the feasibility of applying predictive modeling on short datasets acquired in single patients, paving the way for adding musical elements to brain-computer interface (BCI) applications.
    MeSH term(s) Humans ; Auditory Cortex/physiology ; Music ; Brain Mapping ; Auditory Perception/physiology ; Temporal Lobe/physiology ; Acoustic Stimulation
    Language English
    Publishing date 2023-08-15
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, N.I.H., Extramural
    ZDB-ID 2126776-5
    ISSN 1545-7885 ; 1544-9173
    ISSN (online) 1545-7885
    ISSN 1544-9173
    DOI 10.1371/journal.pbio.3002176
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  6. Article: Dynamics of Oddball Sound Processing: Trial-by-Trial Modeling of ECoG Signals.

    Lecaignard, Françoise / Bertrand, Raphaëlle / Brunner, Peter / Caclin, Anne / Schalk, Gerwin / Mattout, Jérémie

    Frontiers in human neuroscience

    2022  Volume 15, Page(s) 794654

    Abstract: 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 ... ...

    Abstract 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.
    Language English
    Publishing date 2022-02-10
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2425477-0
    ISSN 1662-5161
    ISSN 1662-5161
    DOI 10.3389/fnhum.2021.794654
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  7. Article ; Online: Unexpected sound omissions are signaled in human posterior superior temporal gyrus: an intracranial study.

    Cho, Hohyun / Fonken, Yvonne M / Adamek, Markus / Jimenez, Richard / Lin, Jack J / Schalk, Gerwin / Knight, Robert T / Brunner, Peter

    Cerebral cortex (New York, N.Y. : 1991)

    2023  Volume 33, Issue 14, Page(s) 8837–8848

    Abstract: Context modulates sensory neural activations enhancing perceptual and behavioral performance and reducing prediction errors. However, the mechanism of when and where these high-level expectations act on sensory processing is unclear. Here, we isolate the ...

    Abstract Context modulates sensory neural activations enhancing perceptual and behavioral performance and reducing prediction errors. However, the mechanism of when and where these high-level expectations act on sensory processing is unclear. Here, we isolate the effect of expectation absent of any auditory evoked activity by assessing the response to omitted expected sounds. Electrocorticographic signals were recorded directly from subdural electrode grids placed over the superior temporal gyrus (STG). Subjects listened to a predictable sequence of syllables, with some infrequently omitted. We found high-frequency band activity (HFA, 70-170 Hz) in response to omissions, which overlapped with a posterior subset of auditory-active electrodes in STG. Heard syllables could be distinguishable reliably from STG, but not the identity of the omitted stimulus. Both omission- and target-detection responses were also observed in the prefrontal cortex. We propose that the posterior STG is central for implementing predictions in the auditory environment. HFA omission responses in this region appear to index mismatch-signaling or salience detection processes.
    MeSH term(s) Humans ; Auditory Cortex/physiology ; Wernicke Area ; Acoustic Stimulation ; Evoked Potentials, Auditory/physiology ; Brain Mapping ; Auditory Perception/physiology
    Language English
    Publishing date 2023-06-06
    Publishing country United States
    Document type Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't
    ZDB-ID 1077450-6
    ISSN 1460-2199 ; 1047-3211
    ISSN (online) 1460-2199
    ISSN 1047-3211
    DOI 10.1093/cercor/bhad155
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  8. Article ; Online: Anatomical registration of intracranial electrodes. Robust model-based localization and deformable smooth brain-shift compensation methods.

    Blenkmann, Alejandro Omar / Leske, Sabine Liliana / Llorens, Anaïs / Lin, Jack J / Chang, Edward F / Brunner, Peter / Schalk, Gerwin / Ivanovic, Jugoslav / Larsson, Pål Gunnar / Knight, Robert Thomas / Endestad, Tor / Solbakk, Anne-Kristin

    Journal of neuroscience methods

    2024  Volume 404, Page(s) 110056

    Abstract: Background: Intracranial electrodes are typically localized from post-implantation CT artifacts. Automatic algorithms localizing low signal-to-noise ratio artifacts and high-density electrode arrays are missing. Additionally, implantation of grids/ ... ...

    Abstract Background: Intracranial electrodes are typically localized from post-implantation CT artifacts. Automatic algorithms localizing low signal-to-noise ratio artifacts and high-density electrode arrays are missing. Additionally, implantation of grids/strips introduces brain deformations, resulting in registration errors when fusing post-implantation CT and pre-implantation MR images. Brain-shift compensation methods project electrode coordinates to cortex, but either fail to produce smooth solutions or do not account for brain deformations.
    New methods: We first introduce GridFit, a model-based fitting approach that simultaneously localizes all electrodes' CT artifacts in grids, strips, or depth arrays. Second, we present CEPA, a brain-shift compensation algorithm combining orthogonal-based projections, spring-mesh models, and spatial regularization constraints.
    Results: We tested GridFit on ∼6000 simulated scenarios. The localization of CT artifacts showed robust performance under difficult scenarios, such as noise, overlaps, and high-density implants (<1 mm errors). Validation with data from 20 challenging patients showed 99% accurate localization of the electrodes (3160/3192). We tested CEPA brain-shift compensation with data from 15 patients. Projections accounted for simple mechanical deformation principles with < 0.4 mm errors. The inter-electrode distances smoothly changed across neighbor electrodes, while changes in inter-electrode distances linearly increased with projection distance.
    Comparison with existing methods: GridFit succeeded in difficult scenarios that challenged available methods and outperformed visual localization by preserving the inter-electrode distance. CEPA registration errors were smaller than those obtained for well-established alternatives. Additionally, modeling resting-state high-frequency activity in five patients further supported CEPA.
    Conclusion: GridFit and CEPA are versatile tools for registering intracranial electrode coordinates, providing highly accurate results even in the most challenging implantation scenarios. The methods are implemented in the iElectrodes open-source toolbox.
    MeSH term(s) Humans ; Electroencephalography/methods ; Electrodes, Implanted ; Magnetic Resonance Imaging/methods ; Brain/diagnostic imaging ; Cerebral Cortex/diagnostic imaging ; Electrodes
    Language English
    Publishing date 2024-01-14
    Publishing country Netherlands
    Document type Journal Article ; Review ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't
    ZDB-ID 282721-9
    ISSN 1872-678X ; 0165-0270
    ISSN (online) 1872-678X
    ISSN 0165-0270
    DOI 10.1016/j.jneumeth.2024.110056
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  9. Article ; Online: A motor association area in the depths of the central sulcus.

    Jensen, Michael A / Huang, Harvey / Valencia, Gabriela Ojeda / Klassen, Bryan T / van den Boom, Max A / Kaufmann, Timothy J / Schalk, Gerwin / Brunner, Peter / Worrell, Gregory A / Hermes, Dora / Miller, Kai J

    Nature neuroscience

    2023  Volume 26, Issue 7, Page(s) 1165–1169

    Abstract: Cells in the precentral gyrus directly send signals to the periphery to generate movement and are principally organized as a topological map of the body. We find that movement-induced electrophysiological responses from depth electrodes extend this map ... ...

    Abstract Cells in the precentral gyrus directly send signals to the periphery to generate movement and are principally organized as a topological map of the body. We find that movement-induced electrophysiological responses from depth electrodes extend this map three-dimensionally throughout the gyrus. Unexpectedly, this organization is interrupted by a previously undescribed motor association area in the depths of the midlateral aspect of the central sulcus. This 'Rolandic motor association' (RMA) area is active during movements of different body parts from both sides of the body and may be important for coordinating complex behaviors.
    MeSH term(s) Motor Cortex/physiology ; Movement ; Brain Mapping/methods
    Language English
    Publishing date 2023-05-18
    Publishing country United States
    Document type Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't
    ZDB-ID 1420596-8
    ISSN 1546-1726 ; 1097-6256
    ISSN (online) 1546-1726
    ISSN 1097-6256
    DOI 10.1038/s41593-023-01346-z
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  10. Article ; Online: A neural population selective for song in human auditory cortex.

    Norman-Haignere, Sam V / Feather, Jenelle / Boebinger, Dana / Brunner, Peter / Ritaccio, Anthony / McDermott, Josh H / Schalk, Gerwin / Kanwisher, Nancy

    Current biology : CB

    2022  Volume 32, Issue 7, Page(s) 1470–1484.e12

    Abstract: 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 ... ...

    Abstract 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.
    MeSH term(s) Acoustic Stimulation/methods ; Auditory Cortex/physiology ; Auditory Perception/physiology ; Brain Mapping/methods ; Humans ; Music ; Speech/physiology ; Speech Perception/physiology
    Language English
    Publishing date 2022-02-22
    Publishing country England
    Document type Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S.
    ZDB-ID 1071731-6
    ISSN 1879-0445 ; 0960-9822
    ISSN (online) 1879-0445
    ISSN 0960-9822
    DOI 10.1016/j.cub.2022.01.069
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