1,720,987 research outputs found
Decoding phonemes based on brain activity measured with functional MRI at 7 T
No full textTese de mestrado, Neurociências, Universidade de Lisboa, Faculdade de Medicina, 2022Interfaces cérebro-computador (brain-computer interfaces ou BCI) têm o potencial para oferecer um meio de comunicação para indivíduos que sofrem que síndrome de encarceramento (locked in syndrome). Vários estudos revelam que os mecanismos motores responsáveis pela produção de fonemas individuais estão representados detalhadamente no córtex motor e sensorial. Teoricamente, poderá ser possível descodificar discurso fluente, treinando classificadores com a atividade neuronal de fonemas individuais presente nesta região do córtex. Este estudo investigou a possibilidade de descodificar fonemas produzidos individualmente e em pares (produzidos consecutivamente com um segundo de intervalo) a partir da atividade no córtex sensorial e motor. Quinze sujeitos participaram numa sessão de ressonância magnética funcional 7 T na qual pronunciaram 3 fonemas diferentes e 3 combinações de 2 fonemas. Os fonemas individuais e em pares foram classificados significativamente com support vector machines (SVM). Para além disso, os pares de fonemas foram classificados treinando os classificadores apenas com a atividade de fonemas individuais com uma precisão de 53% (33% probabilidade de acaso). Este resultado é relevante para provar que a atividade de fonemas individuais está presente na atividade de fonemas produzidos consecutivamente. Os resultados da análise SVM searchlight demonstrou que a informação local utilizada para classificar as diferentes condições é bastante limitada, indicando que a informação relevante está amplamente distribuída na região ventral do córtex motor e sensorial. O presente estudo contribui para demonstrar a possibilidade de desenvolver uma BCI baseada em fonemas individuais. É necessário mais investigação para determinar se é possível descodificar palavras com este sistema.Brain-computer interfaces (BCI) can provide a means of communication for people suffering from locked in syndrome (LIS). Several studies have shown that motor programs related to individual phonemes are represented in detail in the sensorimotor cortex. This would theoretically allow for decoding continuous speech by training classifiers based on the activity in sensorimotor cortex related to the production of individual phonemes. We investigated the decodability of trials with individual and paired phonemes (pronounced consecutively with one second interval) using the activity in the sensorimotor cortex. Fifteen participants pronounced 3 different phonemes and their 3 combinations in a 7T functional magnetic resonance imaging experiment. We confirmed that classification of single and paired phonemes was possible using support vector machines (SVM). Importantly, while training a classifier based on single phonemes, we could classify paired phonemes with an accuracy of 53% (significantly above 33% chance level), demonstrating the activity of isolated phonemes to be present when the same phonemes are pronounced in combinations. Results from a SVM searchlight analysis showed that performance of classification based on local information was limited, indicating the information is widely distributed in the ventral sensorimotor cortex. This study shows evidence for the theoretical feasibility of a speech BCI based on training of individual phonemes. Future research is necessary to establish if such a BCI is also capable of classifying whole words
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
Explaining Plasticity after Stroke?
No full textStroke is the leading cause of disability. However, patients may show excellent functional recovery despite severe initial impairment in the first days post stroke. In the past few years there has been an upsurge of studies across neurological disorders that have tried to find indications of beneficial neuronal plasticity, i.e. changes in brain function related to improved neurological functioning, in an attempt to identify new therapeutic targets. Unfortunately, the functional significance of many of the brain changes observed on MRI remains unclear; it has been difficult to relate some of those changes to functional preservation and recovery. The overall aim of this thesis was to investigate changes in brain function related to motor impairment as well as functional recovery in stroke patients (measured with clinical measures and kinematics). In the first chapter we systematically review the current state of longitudinal imaging in stroke until 2008 and assess all studies according to their methodology. In the second chapter we review literature on stroke recovery and plasticity from preclinical studies in rats to RCTs in humans. The focus lied specifically on the defining what upper limb recovery entails as well as exploring what is meant in literature when neural plasticity is referred to. In the 3 experimental papers that follow upper-limb function and brain activity patterns are investigated. In general the brain seems to be quite invariant in response to initial damage beyond 5 weeks after stroke and is nicely able to substitute for residual damage either by a different use of end effector or by more subtle compensation (top down control, using more feedback, more attention). However the massive reduction in function that is seen hours after stroke is more likely not to be a result of actual neuronal damage but to be a result of functional deafferentation of all connected areas to the infarcted area. The goal of future imaging studies should be indeed clearly oriented towards understanding the difference between adaptive processes due to residual damage in the brain as well understanding spontaneous neurological recovery how much of this is alleviation of diaschisis, or some form of repair of neuronal function. What factors define what patients show recovery and what patients will not
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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