1,721,095 research outputs found
Pathophysiological mechanisms of the altered motor command in chronic obstructive pulmonary disease
No full textLa bronchopneumopathie chronique obstructive (BPCO) est une pathologie respiratoire chronique présentant de nombreuses comorbidités. La faiblesse musculaire, caractérisée par une diminution de la force musculaire (de 30 % en moyenne par rapport aux sujets sains) en dehors de tout état de fatigue, est une complication majeure de la pathologie impactant très largement la vie des patients. La production de force dépend de deux processus physiologiques : la capacité du système nerveux à activer le muscle et la capacité du muscle à réaliser une contraction. Ces deux processus sont défaillants dans la BPCO. Cependant, si les altérations du muscle du patient atteint de BPCO sont bien documentées, les mécanismes impliqués dans la production d’une commande motrice non-optimale sont quant à eux mal compris. Le but de ce travail de thèse était donc d’identifier les mécanismes responsables de l’altération de la commande motrice chez les patients atteints de BPCO. Nos travaux ont confirmé l’existence d’une commande motrice réduite, par rapport à des sujets sains. L’utilisation de neuromodulation chez les patients n’a pas permis d’augmenter l’excitabilité corticale et la commande motrice, donc d’évaluer s’il existait des réseaux neuronaux latents chez les BPCO. Nous avons démontré qu’il existait une altération de la connectivité entre les hémisphères cérébraux des patients par rapport à des sujets sains et que l’activation des aires motrices ipsilatérales des patients n’était pas altérée lors de la production de force. Enfin, nous avons montré que les traitements psychoactifs, prescrits pour traiter le syndrome anxio-dépressif, étaient fortement prévalents dans la BPCO. Nous avons montré qu’ils induisent une réduction de l’excitabilité et une augmentation de l’inhibition au niveau cortical, ainsi qu’une altération de la commande motrice. Cependant, l’absence de répercussions sur la force volontaire suggère la présence d’un mécanisme compensatoire.Chronic obstructive pulmonary disease (COPD) is a respiratory pathology associated with several repercussions. The muscle weakness, characterized by a reduction of the muscle strength (30% on average, compared to healthy individuals) without any fatigue, is a major repercussion of the disease. Strength production relies on two physiological processes: the nervous system ability to activate the muscles and the capacity of the muscles to perform a contraction. Both these processes are impaired in COPD. However, while the muscles alterations are well documented, the mechanisms involved in the production of a non-optimal motor command are not fully understood. The aim of this thesis was therefore to identify the mechanisms involved in the motor command alteration in COPD patients. Our work confirmed the existence of a reduced motor command in COPD, compared to healthy subjects. The application of neuromodulation in patients failed to increase cortical excitability and motor command, and consequently to determine whether latent motor networks exists in COPD. We then demonstrated that the connectivity was altered between the brain hemispheres in COPD and that the ipsilateral motor areas activation was preserved in patients during force generation. Finally, we observed that psychoactive medications, prescribed to manage anxiety and depression, we highly prevalent in COPD. The consumption of these medications was associated with reduced excitability and increased inhibition at the cortical level and with an altered motor command. However, the absence of repercussion on strength suggests the existence of a compensatory mechanism
Involvement of central nervous system in peripheral muscle weakness of patients with chronic obstructive pulmonary disease
No full textLa faiblesse des muscles périphériques, définie par une diminution de la force maximale volontaire en dehors de tout état de fatigue neuromusculaire, est une complication fréquente de la broncho-pneumopathie chronique obstructive (BPCO). La force maximale volontaire dépend à la fois des propriétés musculaires périphériques (i.e. volume et architecture musculaire, qualités contractiles) et de la capacité du système nerveux à activer le muscle maximalement. Dans la BPCO, plusieurs travaux ont souligné l'existence paradoxale d'une perte de force maximale volontaire sans altérations musculaires périphériques et sans qu'un déficit d'activation volontaire n'ait clairement été identifié. Pourtant, les patients atteints de BPCO présentent de nombreuses altérations du système nerveux, compatibles avec une capacité d'activation volontaire altérée.L'objectif de ce travail de thèse était donc de tester l'implication du système nerveux dans la faiblesse musculaire de la BPCO et d'en déterminer les mécanismes sous-jacents. Au cours de nos travaux, nous avons mis en évidence une activité corticale diminuée dans la BPCO lors de contractions maximales et sous-maximales volontaires. Nous avons par ailleurs rapporté une perte d'excitabilité du cortex moteur et un déficit d'activation volontaire spécifique aux patients atteints de faiblesse musculaire. Ces résultats sont en accord avec une implication des altérations cérébrales dans la faiblesse musculaire périphérique de la BPCO. Nous sommes ensuite parvenus à identifier une origine potentielle des altérations cérébrales : les désaturations en O2 au cours du sommeil avec mouvements non-rapides des yeux (NREM). Cette hypothèse a été corroborée par l'observation d'un niveau d'activation volontaire réduit chez les patients désatureurs en sommeil NREM. En revanche, aucune répercussion significative n'a pu être observée sur la force maximale volontaire de ces patients, suggérant l'existence d'un mécanisme compensatoire. In fine, nos résultats constituent une avancée importante dans la compréhension du phénomène de faiblesse musculaire, classiquement attribué à la seule perte de masse musculaire. L'implication du système nerveux central dans la faiblesse musculaire ouvre notamment la voie à de nouvelles modalités de prise en charge par des approches spécifiques, dans l'optique de lutter contre la faiblesse musculaire et ses multiples répercussions négatives dans la vie du patient atteint de BPCO.Peripheral muscle weakness, as defined by a reduced voluntary strength outside any state of neuromuscular fatigue, is a common complication of chronic obstructive pulmonary disease (COPD). Maximal voluntary strength is determined by both peripheral muscle properties (i.e. muscle volume and architecture, contractile quality) and the nervous system's ability to activate the muscle maximally. In COPD, many studies highlighted the paradoxical existence of maximal voluntary strength loss without any peripheral muscle impairment, and without a clearly identified voluntary activation deficit. However, patients with COPD exhibited several nervous system alterations compatible with a reduced maximal voluntary activation capacity. The aim of this thesis was to test the nervous system implication in COPD muscle weakness and to determine the involved mechanisms. As major results, we found a reduced cortical activity in COPD during maximal and sub-maximal voluntary contractions. Furthermore, we reported reduced motor cortex excitability and voluntary activation deficit, specifically in patients with muscle weakness. These results are in accordance with an involvement of cortical alterations in COPD muscle weakness. Then, we indentified a potential origin for cortical alterations: O2 desaturation during non-rapid eye movement (NREM) sleep. This hypothesis has been corroborated by the observation of a reduced voluntary activation in patients with NREM sleep desaturation. However, no significant repercussion could have been observed on maximal voluntary strength in these patients, suggesting a compensatory mechanism.Our results are an important step forward in understanding the COPD muscle weakness that was classically attributed to loss of muscle mass only. The involvement of the central nervous system in COPD muscle weakness also brings about new patient care opportunities via tailored approaches, in order to fight against muscle weakness and its deleterious consequences on a patient's life
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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