1,721,001 research outputs found
Power-to-Potential Correlations Identify Markers of Response Inhibition in Human EEG
No full textWhile different ERP markers of response inhibition have been documented in the literature, these are usually identified by comparing either executed- versus inhibited responses (the Go/NoGo task) or correctly inhibited- versus incorrectly executed responses (the stop-signal task). Not only are these comparisons confounded with response execution and/or error commission, but they also ignore other information available that can be used to identify traces of response inhibition in human EEG. We designed a novel task that forces participants to continuously prepare a response and then inhibit it in favor of another response, mostly without the need to actually execute a response. Building on the assumption that more strongly prepared responses also require stronger inhibition to be overruled, we index how strongly a previous response was prepared, through the alpha- and beta power decrease over motor channels, and then correlate this index with the ERP during the following response inhibition period, to identify components that scale with the required strength of inhibition. With this approach, unconfounded by response execution or error commission, we identify a frontal negativity and parietal positivity related to response inhibition. Furthermore, we provide some tentative evidence that this topography can also distinguish between successful and unsuccessful response inhibition when motor confounds are eliminated
Donders Institute for Brain, Cognition and Behaviour
No full textBrain oscillations have been linked to cortical information processing and routing. Thus, those patterns seem to reflect fundamental principles of neuronal communication. Alpha oscillations are thought to moderate the signal flow between brain areas, while gamma oscillations were found to reflect direct computations on the features and their respective cross-area signalling. Both frequency bands have been differentially related to feedback and feedforward processes anatomically implemented across differ-ent cortical layers. To investigate alpha, beta and gamma oscillations during feature selective stimulus processing on a laminar level, a simultaneous EEG-fMRI experiment was set up. Left and right ori-ented Tukey-filtered gratings, served as feature manipulation. Layer specific fMRI signals were obtained through a spatial regression, fitting a feature specific activation template for superficial middle and deep layers to the recorded BOLD activity in V1, V2 and V3. The obtained surrogate feature and layer specific BOLD signals were correlated with source level time-frequency data responses for alpha, beta and gamma bands. Virtual channel data reconstructed using an LCMV beamforming approach was used for that purpose. Due to the novelty of the presented approach, an extensive piloting phase was planned to establish the measurement and analysis protocol. This thesis aims to summerize those findings. It will be demonstrated that all major technical and methodological questions were addressed successfully. Implications for the "real" experiment as well as the potential outcomes of this study are discuss
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Functional role and top-down control of alpha oscillations
No full textL'être humain évolue dans un environnement complexe. À chaque instant de la journée, le cerveau traite un grand nombre d'informations qui nous permettent de prendre des décisions. Les informations à prendre en compte peuvent être externes, c'est-à-dire issues de l'environnement et transmises au cerveau par nos sens, ou internes. Que nous nous concentrions sur les informations externes ou internes, ignorer les informations non pertinentes pourrait être aussi important que d'optimiser le traitement des informations pertinentes. L'objectif principal de cette thèse était de déterminer le mécanisme neuronal qui sous-tend ce processus. Il a été proposé que les oscillations alpha (7-14Hz) soient associées à l'inhibition fonctionnelle et qu'en tant que telles, elles mettent en œuvre la suppression du traitement des informations non pertinentes. Cependant, il existe un débat dans la littérature et le rôle des oscillations alpha dans la protection des processus perceptifs et de plus haut niveau contre les distracteurs n'est pas clair. Nous avons utilisé la magnétoencéphalographie (MEG) pour approfondir cette question. Dans la première étude (chapitre 1), utilisant une tâche de Stroop, nous n'avons pas reproduit l'effet Stoop. Par conséquent, nous n'avons pas trouvé d'oscillations alpha plus élevées dans les régions sensorielles traitant les distracteurs. Nous avons cependant observé des modulations sur le réseau d'attention ventral (VAN) et le réseau du mode par défaut (DMN). Ces deux réseaux ont été respectivement associés à la capture de l'attention par des informations externes et à la concentration interne, et il a été démontré qu'ils sont inhibés pendant les tâches orientées vers un but. En accord avec un rôle inhibiteur des oscillations alpha (et des fréquences plus élevées), nous avons trouvé des oscillations alpha/bêta plus élevées dans ces réseaux pendant la tâche Stroop. Dans notre deuxième étude (chapitre 2), nous avons conçu une tâche plus difficile comprenant des distracteurs à forte saillance, à savoir une tâche Stroop visage/nom. En accord avec un rôle inhibiteur de l'alpha, nous avons observé des oscillations alpha plus élevées sur des régions visuelles élevées, notamment l'aire visuelle des mots (VWFA), lorsque les participants devaient ignorer des noms. Dans notre dernière étude (chapitre 3), nous avons utilisé une tâche de raisonnement nécessitant de surmonter un biais perceptif, c'est-à-dire d'inhiber le cortex visuel. Nous avons montré des oscillations alpha plus élevées sur le cortex temporal gauche et le VAN lorsque les participants devaient surmonter un tel biais. Dans l'ensemble, ces résultats indiquent que les oscillations alpha (mais aussi bêta) pourraient mettre en œuvre l'inhibition fonctionnelle dans un réseau étendu, mais que leur modulation dans les zones sensorielles pourrait dépendre de paramètres de la tâche tels que la difficulté de la tâche ou la saillance du distracteur.Humans evolve in a complex environment. At each moment of a day, the brain processes a lot of information allowing us to make decisions. Information to consider can be external, i.e., from the environment and transmitted to the brain through our senses, or internal. Whether we focus on external or internal information, ignoring irrelevant information might be as important as optimizing the processing of relevant information. The main goal of this thesis was to determine the neural mechanism underlying this process. Alpha oscillations (7-14Hz) have been proposed to be associated with functional inhibition and as such to implement the suppression of the processing of irrelevant information. However, there is a debate in the literature and the role of alpha oscillations in protecting perceptual and higher-level processes from distractors is unclear. We used magnetoencephalography (MEG) to further investigate this question. In the first study (chapter 1), using a Stroop task, we did not replicate the Stoop effect. Accordingly, we did not find higher alpha oscillations over sensory regions processing the distractors. We however we observed modulations over the ventral attention network (VAN) and the default mode network (DMN). These two networks have been respectively associated with attention capture by external information and internal focus and shown to be inhibited during goal-driven tasks. In line with an inhibitory role of alpha oscillations (and higher frequencies), we found higher alpha/beta oscillations in these networks during the Stroop task. In our second study (chapter 2), we designed a more challenging task including high salience distractors, namely a face/name Stroop task. In line with an inhibitory role of alpha, we observed higher alpha oscillations over high visual regions, namely the visual word form area (VWFA), when participants had to ignore names. In our last study (chapter 3), we used a reasoning task requiring to overcome a perceptual bias, i.e., to inhibit the visual cortex. We showed higher alpha oscillations over the left temporal cortex and the VAN when participants had to overcome such bias. Overall, these results indicate that alpha (but also beta) oscillations might implement functional inhibition in a widespread network but their modulation in sensory areas might rely on task parameters such as task difficulty or distractor salience
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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