1,482 research outputs found

    Design and Evaluation of a Hardware System for Online Signal Processing within Mobile Brain-Computer Interfaces

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    Brain-Computer Interfaces (BCIs) sind innovative Systeme, die eine direkte Kommunikation zwischen dem Gehirn und externen Geräten ermöglichen. Diese Schnittstellen haben sich zu einer transformativen Lösung nicht nur für Menschen mit neurologischen Verletzungen entwickelt, sondern auch für ein breiteres Spektrum von Menschen, das sowohl medizinische als auch nicht-medizinische Anwendungen umfasst. In der Vergangenheit hat die Herausforderung, dass neurologische Verletzungen nach einer anfänglichen Erholungsphase statisch bleiben, die Forscher dazu veranlasst, innovative Wege zu beschreiten. Seit den 1970er Jahren stehen BCIs an vorderster Front dieser Bemühungen. Mit den Fortschritten in der Forschung haben sich die BCI-Anwendungen erweitert und zeigen ein großes Potenzial für eine Vielzahl von Anwendungen, auch für weniger stark eingeschränkte (zum Beispiel im Kontext von Hörelektronik) sowie völlig gesunde Menschen (zum Beispiel in der Unterhaltungsindustrie). Die Zukunft der BCI-Forschung hängt jedoch auch von der Verfügbarkeit zuverlässiger BCI-Hardware ab, die den Einsatz in der realen Welt gewährleistet. Das im Rahmen dieser Arbeit konzipierte und implementierte CereBridge-System stellt einen bedeutenden Fortschritt in der Brain-Computer-Interface-Technologie dar, da es die gesamte Hardware zur Erfassung und Verarbeitung von EEG-Signalen in ein mobiles System integriert. Die Architektur der Verarbeitungshardware basiert auf einem FPGA mit einem ARM Cortex-M3 innerhalb eines heterogenen ICs, was Flexibilität und Effizienz bei der EEG-Signalverarbeitung gewährleistet. Der modulare Aufbau des Systems, bestehend aus drei einzelnen Boards, gewährleistet die Anpassbarkeit an unterschiedliche Anforderungen. Das komplette System wird an der Kopfhaut befestigt, kann autonom arbeiten, benötigt keine externe Interaktion und wiegt einschließlich der 16-Kanal-EEG-Sensoren nur ca. 56 g. Der Fokus liegt auf voller Mobilität. Das vorgeschlagene anpassbare Datenflusskonzept erleichtert die Untersuchung und nahtlose Integration von Algorithmen und erhöht die Flexibilität des Systems. Dies wird auch durch die Möglichkeit unterstrichen, verschiedene Algorithmen auf EEG-Daten anzuwenden, um unterschiedliche Anwendungsziele zu erreichen. High-Level Synthesis (HLS) wurde verwendet, um die Algorithmen auf das FPGA zu portieren, was den Algorithmenentwicklungsprozess beschleunigt und eine schnelle Implementierung von Algorithmusvarianten ermöglicht. Evaluierungen haben gezeigt, dass das CereBridge-System in der Lage ist, die gesamte Signalverarbeitungskette zu integrieren, die für verschiedene BCI-Anwendungen erforderlich ist. Darüber hinaus kann es mit einer Batterie von mehr als 31 Stunden Dauerbetrieb betrieben werden, was es zu einer praktikablen Lösung für mobile Langzeit-EEG-Aufzeichnungen und reale BCI-Studien macht. Im Vergleich zu bestehenden Forschungsplattformen bietet das CereBridge-System eine bisher unerreichte Leistungsfähigkeit und Ausstattung für ein mobiles BCI. Es erfüllt nicht nur die relevanten Anforderungen an ein mobiles BCI-System, sondern ebnet auch den Weg für eine schnelle Übertragung von Algorithmen aus dem Labor in reale Anwendungen. Im Wesentlichen liefert diese Arbeit einen umfassenden Entwurf für die Entwicklung und Implementierung eines hochmodernen mobilen EEG-basierten BCI-Systems und setzt damit einen neuen Standard für BCI-Hardware, die in der Praxis eingesetzt werden kann.Brain-Computer Interfaces (BCIs) are innovative systems that enable direct communication between the brain and external devices. These interfaces have emerged as a transformative solution not only for individuals with neurological injuries, but also for a broader range of individuals, encompassing both medical and non-medical applications. Historically, the challenge of neurological injury being static after an initial recovery phase has driven researchers to explore innovative avenues. Since the 1970s, BCIs have been at one forefront of these efforts. As research has progressed, BCI applications have expanded, showing potential in a wide range of applications, including those for less severely disabled (e.g. in the context of hearing aids) and completely healthy individuals (e.g. entertainment industry). However, the future of BCI research also depends on the availability of reliable BCI hardware to ensure real-world application. The CereBridge system designed and implemented in this work represents a significant leap forward in brain-computer interface technology by integrating all EEG signal acquisition and processing hardware into a mobile system. The processing hardware architecture is centered around an FPGA with an ARM Cortex-M3 within a heterogeneous IC, ensuring flexibility and efficiency in EEG signal processing. The modular design of the system, consisting of three individual boards, ensures adaptability to different requirements. With a focus on full mobility, the complete system is mounted on the scalp, can operate autonomously, requires no external interaction, and weighs approximately 56g, including 16 channel EEG sensors. The proposed customizable dataflow concept facilitates the exploration and seamless integration of algorithms, increasing the flexibility of the system. This is further underscored by the ability to apply different algorithms to recorded EEG data to meet different application goals. High-Level Synthesis (HLS) was used to port algorithms to the FPGA, accelerating the algorithm development process and facilitating rapid implementation of algorithm variants. Evaluations have shown that the CereBridge system is capable of integrating the complete signal processing chain required for various BCI applications. Furthermore, it can operate continuously for more than 31 hours with a 1800mAh battery, making it a viable solution for long-term mobile EEG recording and real-world BCI studies. Compared to existing research platforms, the CereBridge system offers unprecedented performance and features for a mobile BCI. It not only meets the relevant requirements for a mobile BCI system, but also paves the way for the rapid transition of algorithms from the laboratory to real-world applications. In essence, this work provides a comprehensive blueprint for the development and implementation of a state-of-the-art mobile EEG-based BCI system, setting a new benchmark in BCI hardware for real-world applicability

    Visual neuroscience : A brain area tuned for processing social interactions

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    Socialising with others is part of everyday life. A new study demonstrates that a brain area specialised for visual body perception is attuned to processing social interactions between two people. Intriguingly, this area is lateralised in the left hemisphere

    HOW DO FOLLOWERS EXPERIENCE SHARED LEADERSHIP AS A LIVED EXPERIENCE? Understanding the relationality, processes and practices informing such collaboration.

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    How do followers experience shared leadership as a lived experience? Understanding the relationality, processes and practices informing such collaboration. Within shared leadership research culture, the aspiration is to explore “leadership as a dynamic interactive influence process”’ at the group level, supporting goal achievement (Pearce and Conger, 2003, P.1). However, the motivation of much research has focused on performance improvement, whereby discrete leadership variables are examined, using reductionist methods, to determine relevant linkages to team effectiveness (Denis et al., 2012. See also Fairhurst et.al, 2020). In expanding understanding of shared leadership from a follower perspective, enabling a fuller appreciation of how that has been experienced and operationalised over time, an immersive, participatory action research study was conducted, to facilitate a processual view of shared leadership; one that embraces relational aspects of shared leadership and considers its dynamic emergence within a hierarchical leadership setting. Unconventionally, Relational Cultural Theory has been applied to enable a more meaningful and nuanced consideration of this leadership phenomenon (Fletcher, 2012). This expanded consideration of shared leadership has produced four main findings: • The follower “voice” has been meaningfully expressed regarding experiences and actions, occurring throughout such collaboration. • A more processual understanding of the shared leadership undertaking itself, reveals how the cultivation of interdependence enables the dynamic operationalisation of expertise in relational and reciprocal ways. • The shifting nature of power dynamics has been explicated, as well as recognising the degree of interdependence occurring between followers and their leaders. • Learning History methodology was innovatively applied to facilitate a more processual understanding of shared leadership, facilitating new theoretical and practical understanding. This study challenges some of the negative connotations that may surround conceptualisations of followers and followership (Uhl-Bien, 2018), as well as actively elevating and emotionalising their experience, which is uncommon (Reitz, 2014). Finally, this study, through its positive conceptualisation of share leadership effectively challenges the myth of individual achievement that pervades much organisational life (Miller, 2012)

    Tau pathology in Alzheimer's disease and other dementias : translational approach from in vitro autoradiography to in vivo PET imaging

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    Tauopathies, including Alzheimer's disease (AD), corticobasal degeneration (CBD), and progressive supranuclear palsy (PSP), are complex neurodegenerative disorders characterized by the pathological accumulation of tau proteins in the brain. These often overlapping disorders, with intricate pathologies and growing prevalence, lack definitive treatments, highlighting the necessity for advanced research. Positron emission tomography (PET) imaging aids in the diagnosis and monitoring of diseases, by providing in vivo insights into pathological features. This thesis focused on deciphering the binding properties and brain regional distribution of PET tracers for accurate disease differentiation. Spanning four studies, we aimed to bridge in vitro and in vivo PET data to investigate tau pathology and its association with dementia-related markers such as reactive astrogliosis, peripheral inflammation, and dopaminergic dysfunction. The 2nd generation tau PET tracers, 3H-MK6240 and 3H-PI2620, demonstrated high affinity and specificity in AD post-mortem brain tissues, especially in early-onset AD, compared to controls. 3H-PI2620, 3H-MK6240, and 3HRO948 displayed similar binding patterns in AD tissue, with multiple binding sites and equivalent high affinities (Papers I and II). 3H-PI2620 showed specificity in CBD and PSP tissues, in contrast to 3H-MK6240. However, differentiating CBD from PSP brains with 3H-PI2620 remained challenging in multiple brain regions, potentially due to complex tracer-target interactions (Papers II and III). Reactive astrogliosis PET tracers 3H-Deprenyl and 3H-BU99008 bound primarily to stable distinct high-affinity binding sites in AD, CBD and PSP, but also to transient binding sites, differing by brain region and condition. This pattern implied that these tracers may interact with similar or diverse subtypes or populations of astrocytes, expressing varying ratios of transient sites, which may vary depending on the brain location and the disease (Paper III). Using 3H-FEPE2I, we delineated a reduction in dopamine transporter (DAT) levels within the putamen across CBD, PSP and Parkinson's Disease (PD) brains. Concomitantly, elevated 3H-Raclopride binding reflected higher dopamine D2 receptor (D2R) levels in PSP and PD. Nonetheless, our observations underscored the heterogeneity inherent to these neurodegenerative pathologies, emphasizing the criticality of individual variability in neuropathological manifestations (Paper III). Lastly, we investigated late middle-aged cognitively unimpaired Hispanic individuals, in dichotomous groups of in vivo amyloid-β (Aβ) PET (18F-Florbetaben) and plasma neurofilament light (NfL) biomarkers. Our findings suggest that elevated plasma inflammation and tau burden as measured by 18FMK6240, can be detected at early preclinical stages of AD, offering potential for early diagnosis (Paper IV). This thesis underscored the importance of PET imaging in advancing our understanding of tauopathies. The innovative use of multiple PET tracers provided crucial insights into their potential use in clinics to distinguish pathological features of AD, CBD and PSP. The findings emphasized the need for more studies applying a multifaceted approach to studying and managing these complex neurodegenerative disorders, combining advanced imaging techniques with a broad spectrum of biological markers

    Automatic, early color-specific neural responses to object color knowledge

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    Some familiar objects are associated with specific colors, e.g., rubber ducks with yellow. Whether and at what stage neural responses occur to these color associations remain open questions. We recorded frequency-tagged electroencephalogram (EEG) responses to periodic presentations of yellow-associated objects, shown among sequences of non-periodic blue-, red-, and green- associated objects. Both color and grayscale versions of the objects elicited yellow-specific responses, indicating an automatic activation of color knowledge from object shape. Follow-up experiments replicated these effects with green-specific responses, and demonstrated modulated responses for incongruent color/object associations. Importantly, the onset of color-specific responses was as early to grayscale as actually colored stimuli (before 100 ms), the latter additionally eliciting a conventional later response (approximately 140-230 ms) to actual stimulus color. This suggests that the neural representation of familiar objects includes both diagnostic shape and color properties, such that shape can elicit associated color-specific responses before actual color-specific responses occur

    Converging evidence that left extrastriate body area supports visual sensitivity to social interactions

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    Navigating our complex social world requires processing the interactions we observe. Recent psychophysical and neuroimaging studies provide parallel evidence that the human visual system may be attuned to efficiently perceive dyadic interactions. This work implies, but has not yet demonstrated, that activity in body-selective cortical regions causally supports efficient visual perception of interactions. We adopt a multi-method approach to close this important gap. First, using a large fMRI dataset (N=92), we found that the left-hemisphere Extrastriate Body Area (EBA) responds more to face-to-face than non-facing dyads. Second, we replicated a behavioural marker of visual sensitivity to interactions: categorisation of facing dyads is more impaired by inversion than non-facing dyads. Third, in a pre-registered experiment, we used fMRI-guided transcranial magnetic stimulation to show that online stimulation of the left EBA, but not a nearby control region, abolishes this selective inversion effect. Activity in left EBA, thus, causally supports the efficient perception of social interactions

    2023 SPARC Book Of Abstracts

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    The neural basis of semantic processing across comprehension contexts

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    Current neurobiological models of semantic cognition have been predominately derived from studies of single-words or sentences which may provide an impoverished estimate of how semantic processing occurs in real-world contexts. Studies that make use of more ecologically valid stimuli such as natural language or narratives suggest that, counter to the hub-and-spoke framework in which the anterior temporal lobe (ATL) serves as a graded hub integrating information from proximal sensorimotor spokes, the semantic system displays voxel-wise category specialization tiled across a large, distributed network. A complicating factor in reconciling these seemingly conflicting claims is the over-reliance on concrete conceptual knowledge in describing the organization of the semantic system. A recent theoretical account argues that social knowledge, like other types of semantic knowledge, is processed within the ventrolateral ATL, but this claim has not been tested using naturalistic stimuli, which better sample abstract social knowledge, including pragmatic inference. This thesis investigates the organization of the semantic system across multiple scales, from isolated words to multimodal narratives, and across multiple types of semantic conceptual knowledge, from concrete to abstract. Using comprehension of concrete words as a starting point, the first study describes a critical examination of specialization within the semantic system for taxonomic (dog – bear) and thematic (dog – leash) relations using intracranial EEG recordings from an array of depth electrodes within ATL, inferior parietal lobule (IPL), and two regions within the semantic control network, inferior frontal gyrus (IFG) and posterior middle temporal gyrus (pMTG). Moving across the context and conceptual scale to build upon this work, the second study investigated how the concrete and abstract lexical and semantic properties of single-words, akin to those that informed the hub-and-spoke model, are processed in a complex, complete narrative presented to participants during fMRI scanning. In doing so, this study enabled comparisons between prior studies of isolated words and naturalistic work, thus moving toward an integrated cross-scale account of semantic cognition. Using the same neuroimaging data, the third study extended this work to investigate how context contributes to the construction of meaning by studying how the semantic and social cognitive systems are engaged by social and pragmatic sentence-level content. This enabled a direct, naturalistic test of the claim that social knowledge is housed within the semantic system. The fourth study investigated shared processing between social and semantic systems using fMRI data collected during movie-viewing, which captures the multimodal environment in which social knowledge is exchanged. The results of these studies collectively demonstrate that the semantic and social systems are differentially engaged across the scales investigated here. Concrete conceptual relations engage one (or more) specialized hubs within the semantic system, whereas processing of naturalistic verbal and event content co-varies with activation in large brain networks. There is evidence of functional gradations within ATL that are differentially sensitive to the demands of narrative comprehension – the anterior superior temporal gyrus (i.e., dorsolateral subregion) and anterior fusiform (i.e., ventral subregion) appear to be particularly sensitive to the quantity and informativeness of external input whereas the anterior middle and inferior temporal gyri (i.e., ventrolateral subregion) appear to be engaged by internal, or endogenous, semantic processing during narrative comprehension. Engagement of this same ventrolateral subregion is observed in response to social word and sentence content, providing support for the claim that social processing is subsumed within the semantic system. Taken together, the results suggest an extension to the current neurobiological model of semantic cognition that accommodates comprehension contexts. The studies undertaken as part of this thesis build upon the existing concept-level frameworks towards a narrative-level framework of semantic cognition

    Brain Signatures of Embodied Semantics and Language: A Consensus Paper

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    According to embodied theories (including embodied, embedded, extended, enacted, situated, and grounded approaches to cognition), language representation is intrinsically linked to our interactions with the world around us, which is reflected in specific brain signatures during language processing and learning. Moving on from the original rivalry of embodied vs. amodal theories, this consensus paper addresses a series of carefully selected questions that aim at determining when and how rather than whether motor and perceptual processes are involved in language processes. We cover a wide range of research areas, from the neurophysiological signatures of embodied semantics, e.g., event-related potentials and fields as well as neural oscillations, to semantic processing and semantic priming effects on concrete and abstract words, to first and second language learning and, finally, the use of virtual reality for examining embodied semantics. Our common aim is to better understand the role of motor and perceptual processes in language representation as indexed by language comprehension and learning. We come to the consensus that, based on seminal research conducted in the field, future directions now call for enhancing the external validity of findings by acknowledging the multimodality, multidimensionality, flexibility and idiosyncrasy of embodied and situated language and semantic processes

    Consensus Paper: Current Perspectives on Abstract Concepts and Future Research Directions

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    Abstract concepts are relevant to a wide range of disciplines, including cognitive science, linguistics, psychology, cognitive, social, and affective neuroscience, and philosophy. This consensus paper synthesizes the work and views of researchers in the field, discussing current perspectives on theoretical and methodological issues, and recommendations for future research. In this paper, we urge researchers to go beyond the traditional abstract-concrete dichotomy and consider the multiple dimensions that characterize concepts (e.g., sensorimotor experience, social interaction, conceptual metaphor), as well as the mediating influence of linguistic and cultural context on conceptual representations. We also promote the use of interactive methods to investigate both the comprehension and production of abstract concepts, while also focusing on individual differences in conceptual representations. Overall, we argue that abstract concepts should be studied in a more nuanced way that takes into account their complexity and diversity, which should permit us a fuller, more holistic understanding of abstract cognition
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