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  • 1
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    Towards a more robust non-invasive assessment of functional connectivity
    MIT Press ; 2024
    In:  Imaging Neuroscience ( 2024-03-11)
    Details
    In: Imaging Neuroscience, MIT Press, ( 2024-03-11)
    Abstract: Non-invasive evaluation of functional connectivity, based on source-reconstructed estimates of phase-difference-based metrics, is notoriously non-robust. This is due to a combination of factors, ranging from a misspecification of seed regions to suboptimal baseline assumptions, and residual signal leakage. In this work, we propose a new analysis scheme of source level phase-difference-based connectivity, which is aimed at optimizing the detection of interacting brain regions. Our approach is based on the combined use of sensor subsampling and dual-source beamformer estimation of all-to-all connectivity on a prespecified dipolar grid. First, a pairwise two-dipole model, to account for reciprocal leakage in the estimation of the localized signals, allows for a usable approximation of the pairwise bias in connectivity due to residual leakage of ‘third party’ noise. Secondly, using sensor array subsampling, the recreation of multiple connectivity maps using different subsets of sensors allows for the identification of consistent spatially localized peaks in the 6-dimensional connectivity maps, indicative of true brain region interactions. These steps are combined with the subtraction of null coherence estimates to obtain the final coherence maps. With extensive simulations, we compared different analysis schemes for their detection rate of connected dipoles, as a function of signal-to-noise ratio, phase difference and connection strength. We demonstrate superiority of the proposed analysis scheme in comparison to single-dipole models, or an approach that discards the zero phase difference component of the connectivity. We conclude that the proposed pipeline allows for a more robust identification of functional connectivity in experimental data, opening up new possibilities to study brain networks with mechanistically inspired connectivity measures in cognition and in the clinic.
    Type of Medium: Online Resource
    ISSN: 2837-6056
    URL: Article
    DOI: 10.1162/imag_a_00119
    Language: English
    Publisher: MIT Press
    Publication Date: 2024
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  • 2
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    Familiarity modulates neural tracking of sung and spoken utterances
    Elsevier BV ; 2022
    In:  NeuroImage Vol. 252 ( 2022-05), p. 119049-
    Details
    In: NeuroImage, Elsevier BV, Vol. 252 ( 2022-05), p. 119049-
    Type of Medium: Online Resource
    ISSN: 1053-8119
    URL: Article
    DOI: 10.1016/j.neuroimage.2022.119049
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2022
    detail.hit.zdb_id: 1471418-8
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  • 3
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    Sensory Modality-Independent Activation of the Brain Network for Language
    Society for Neuroscience ; 2020
    In:  The Journal of Neuroscience Vol. 40, No. 14 ( 2020-04-01), p. 2914-2924
    Details
    In: The Journal of Neuroscience, Society for Neuroscience, Vol. 40, No. 14 ( 2020-04-01), p. 2914-2924
    Abstract: The meaning of a sentence can be understood, whether presented in written or spoken form. Therefore, it is highly probable that brain processes supporting language comprehension are at least partly independent of sensory modality. To identify where and when in the brain language processing is independent of sensory modality, we directly compared neuromagnetic brain signals of 200 human subjects (102 males) either reading or listening to sentences. We used multiset canonical correlation analysis to align individual subject data in a way that boosts those aspects of the signal that are common to all, allowing us to capture word-by-word signal variations, consistent across subjects and at a fine temporal scale. Quantifying this consistency in activation across both reading and listening tasks revealed a mostly left-hemispheric cortical network. Areas showing consistent activity patterns included not only areas previously implicated in higher-level language processing, such as left prefrontal, superior and middle temporal areas, and anterior temporal lobe, but also parts of the control network as well as subcentral and more posterior temporal-parietal areas. Activity in this supramodal sentence-processing network starts in temporal areas and rapidly spreads to the other regions involved. The findings indicate not only the involvement of a large network of brain areas in supramodal language processing but also that the linguistic information contained in the unfolding sentences modulates brain activity in a word-specific manner across subjects. SIGNIFICANCE STATEMENT The brain can extract meaning from written and spoken messages alike. This requires activity of both brain circuits capable of processing sensory modality-specific aspects of the input signals as well as coordinated brain activity to extract modality-independent meaning from the input. Using traditional methods, it is difficult to disentangle modality-specific activation from modality-independent activation. In this work, we developed and applied a multivariate methodology that allows for a direct quantification of sensory modality-independent brain activity, revealing fast activation of a wide network of brain areas, both including and extending beyond the core network for language.
    Type of Medium: Online Resource
    ISSN: 0270-6474 , 1529-2401
    URL: Article
    DOI: 10.1523/JNEUROSCI.2271-19.2020
    Language: English
    Publisher: Society for Neuroscience
    Publication Date: 2020
    detail.hit.zdb_id: 1475274-8
    SSG: 12
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  • 4
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    Delta-Band Neural Responses to Individual Words Are Modulated by Sentence Processing
    Society for Neuroscience ; 2023
    In:  The Journal of Neuroscience Vol. 43, No. 26 ( 2023-06-28), p. 4867-4883
    Details
    In: The Journal of Neuroscience, Society for Neuroscience, Vol. 43, No. 26 ( 2023-06-28), p. 4867-4883
    Abstract: To understand language, we need to recognize words and combine them into phrases and sentences. During this process, responses to the words themselves are changed. In a step toward understanding how the brain builds sentence structure, the present study concerns the neural readout of this adaptation. We ask whether low-frequency neural readouts associated with words change as a function of being in a sentence. To this end, we analyzed an MEG dataset by Schoffelen et al. (2019) of 102 human participants (51 women) listening to sentences and word lists, the latter lacking any syntactic structure and combinatorial meaning. Using temporal response functions and a cumulative model-fitting approach, we disentangled delta- and theta-band responses to lexical information (word frequency), from responses to sensory and distributional variables. The results suggest that delta-band responses to words are affected by sentence context in time and space, over and above entropy and surprisal. In both conditions, the word frequency response spanned left temporal and posterior frontal areas; however, the response appeared later in word lists than in sentences. In addition, sentence context determined whether inferior frontal areas were responsive to lexical information. In the theta band, the amplitude was larger in the word list condition ∼100 milliseconds in right frontal areas. We conclude that low-frequency responses to words are changed by sentential context. The results of this study show how the neural representation of words is affected by structural context and as such provide insight into how the brain instantiates compositionality in language. SIGNIFICANCE STATEMENT Human language is unprecedented in its combinatorial capacity: we are capable of producing and understanding sentences we have never heard before. Although the mechanisms underlying this capacity have been described in formal linguistics and cognitive science, how they are implemented in the brain remains to a large extent unknown. A large body of earlier work from the cognitive neuroscientific literature implies a role for delta-band neural activity in the representation of linguistic structure and meaning. In this work, we combine these insights and techniques with findings from psycholinguistics to show that meaning is more than the sum of its parts; the delta-band MEG signal differentially reflects lexical information inside and outside sentence structures.
    Type of Medium: Online Resource
    ISSN: 0270-6474 , 1529-2401
    URL: Article
    DOI: 10.1523/JNEUROSCI.0964-22.2023
    Language: English
    Publisher: Society for Neuroscience
    Publication Date: 2023
    detail.hit.zdb_id: 1475274-8
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  • 5
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    The frequency gradient of human resting-state brain oscillations follows cortical hierarchies
    eLife Sciences Publications, Ltd ; 2020
    In:  eLife Vol. 9 ( 2020-08-21)
    Details
    In: eLife, eLife Sciences Publications, Ltd, Vol. 9 ( 2020-08-21)
    Abstract: The human cortex is characterized by local morphological features such as cortical thickness, myelin content, and gene expression that change along the posterior-anterior axis. We investigated if some of these structural gradients are associated with a similar gradient in a prominent feature of brain activity - namely the frequency of oscillations. In resting-state MEG recordings from healthy participants (N = 187) using mixed effect models, we found that the dominant peak frequency in a brain area decreases significantly along the posterior-anterior axis following the global hierarchy from early sensory to higher order areas. This spatial gradient of peak frequency was significantly anticorrelated with that of cortical thickness, representing a proxy of the cortical hierarchical level. This result indicates that the dominant frequency changes systematically and globally along the spatial and hierarchical gradients and establishes a new structure-function relationship pertaining to brain oscillations as a core organization that may underlie hierarchical specialization in the brain.
    Type of Medium: Online Resource
    ISSN: 2050-084X
    URL: Article
    DOI: 10.7554/eLife.53715
    Language: English
    Publisher: eLife Sciences Publications, Ltd
    Publication Date: 2020
    detail.hit.zdb_id: 2687154-3
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  • 6
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    N°74 – Estimating the influence of stroke lesions on MEG source reconstruction
    Elsevier BV ; 2023
    In:  Clinical Neurophysiology Vol. 150 ( 2023-06), p. e95-e96
    Details
    In: Clinical Neurophysiology, Elsevier BV, Vol. 150 ( 2023-06), p. e95-e96
    Type of Medium: Online Resource
    ISSN: 1388-2457
    URL: Article
    DOI: 10.1016/j.clinph.2023.03.081
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2023
    detail.hit.zdb_id: 1499934-1
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  • 7
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    Alpha Oscillations Shape Sensory Representation and Perceptual Sensitivity
    Society for Neuroscience ; 2021
    In:  The Journal of Neuroscience Vol. 41, No. 46 ( 2021-11-17), p. 9581-9592
    Details
    In: The Journal of Neuroscience, Society for Neuroscience, Vol. 41, No. 46 ( 2021-11-17), p. 9581-9592
    Abstract: Alpha activity (8–14 Hz) is the dominant rhythm in the awake brain and is thought to play an important role in setting the internal state of the brain. Previous work has associated states of decreased alpha power with enhanced neural excitability. However, evidence is mixed on whether and how such excitability enhancement modulates sensory signals of interest versus noise differently, and what, if any, are the consequences for subsequent perception. Here, human subjects (male and female) performed a visual detection task in which we manipulated their decision criteria in a blockwise manner. Although our manipulation led to substantial criterion shifts, these shifts were not reflected in prestimulus alpha band changes. Rather, lower prestimulus alpha power in occipital-parietal areas improved perceptual sensitivity and enhanced information content decodable from neural activity patterns. Additionally, oscillatory alpha phase immediately before stimulus presentation modulated accuracy. Together, our results suggest that alpha band dynamics modulate sensory signals of interest more strongly than noise. SIGNIFICANCE STATEMENT The internal state of our brain fluctuates, giving rise to variability in perception and action. Neural oscillations, most prominently in the alpha band, have been suggested to play a role in setting this internal state. Here, we show that ongoing alpha band activity in occipital-parietal regions predicts the quality of visual information decodable in neural activity patterns and subsequently the human observer's sensitivity in a visual detection task. Our results provide comprehensive evidence that visual representation is modulated by ongoing alpha band activity and advance our understanding on how, when faced with unchanging external stimuli, internal neural fluctuations influence perception and behavior.
    Type of Medium: Online Resource
    ISSN: 0270-6474 , 1529-2401
    URL: Article
    DOI: 10.1523/JNEUROSCI.1114-21.2021
    Language: English
    Publisher: Society for Neuroscience
    Publication Date: 2021
    detail.hit.zdb_id: 1475274-8
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  • 8
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    The Influence of Alpha Frequency on Temporal Binding across the Senses: Response to the Special Focus
    MIT Press ; 2024
    In:  Journal of Cognitive Neuroscience Vol. 36, No. 4 ( 2024-04-01), p. 730-733
    Details
    In: Journal of Cognitive Neuroscience, MIT Press, Vol. 36, No. 4 ( 2024-04-01), p. 730-733
    Abstract: The papers collected in this Special Focus, prompted by S. Buergers and U. Noppeney [The role of alpha oscillations in temporal binding within and across the senses. Nature Human Behaviour, 6, 732–742, 2022], have raised several interesting ideas, arguments, and empirical results relating to the alpha temporal resolution hypothesis. Here we briefly respond to these, and in the process emphasize four challenges for future research: defining the scope and limitation of the hypothesis; developing experimental paradigms and study designs that rigorously test its tenets; decomposing the scalp-level signal and isolating underlying neural circuits; and bringing uniformity to the current diversity of analysis and statistical methods. Addressing these challenges will facilitate the progression from merely correlating alpha frequency with various perceptual phenomena to establishing whether and (if so) how alpha frequency influences sensory integration and segregation.
    Type of Medium: Online Resource
    ISSN: 0898-929X , 1530-8898
    URL: Article
    DOI: 10.1162/jocn_a_02112
    Language: English
    Publisher: MIT Press
    Publication Date: 2024
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    SSG: 7,11
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  • 9
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    Parallel or sequential? Decoding conceptual and phonological/phonetic information from MEG signals during language production
    Informa UK Limited ; 2023
    In:  Cognitive Neuropsychology
    Details
    In: Cognitive Neuropsychology, Informa UK Limited
    Type of Medium: Online Resource
    ISSN: 0264-3294 , 1464-0627
    URL: Article
    DOI: 10.1080/02643294.2023.2283239
    Language: English
    Publisher: Informa UK Limited
    Publication Date: 2023
    detail.hit.zdb_id: 226406-7
    detail.hit.zdb_id: 1475589-0
    SSG: 5,2
    SSG: 7,11
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  • 10
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    Estimating the influence of stroke lesions on MEG source reconstruction
    Elsevier BV ; 2022
    In:  NeuroImage Vol. 260 ( 2022-10), p. 119422-
    Details
    In: NeuroImage, Elsevier BV, Vol. 260 ( 2022-10), p. 119422-
    Type of Medium: Online Resource
    ISSN: 1053-8119
    URL: Article
    DOI: 10.1016/j.neuroimage.2022.119422
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2022
    detail.hit.zdb_id: 1471418-8
    SSG: 5,2
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