1,720,983 research outputs found
ACES:Automated Correlation of Electric field strength and Stimulation effects for non-invasive brain stimulation
Full text linkMultiple sources of (protocol, inter-individual) variability contribute to the limited reliability of non-invasive brain stimulation (NIBS) findings [1]. Meta-analytical techniques could potentially even out such variability, but are hampered by the large parameter space involved [2]. Wischnewski and colleauges [3] recently proposed a partial solution, suggesting a novel approach to aggregate transcranial direct current stimulation (tDCS) studies using various montages and stimulation parameters. They simulated the electric field in a common head model using SimNIBS [4], an open source software which allows the user to model the fields induced by a specific NIBS protocol in a particular head model. The stimulation protocols were hence transformed to sets of merely quantitatively differing values in a common brain space, rendering them directly comparable. Subsequently, the electric field magnitude (|E|) values from these simulations were correlated to the effect sizes across studies, identifying loci where electric field magnitude was associated with an impact on the outcome of interest (i.e., working memory performance). An analogous method could in principle handle inter-subject variability, i.e., overcome morphological differences or aggregate data from different montages at the within-study level (see below). To facilitate adoption of this approach, we introduce Automated Correlation of Electric field strength and Stimulation effect (ACES), a MATLAB algorithm enabling the aggregation of NIBS findings on the meta-analytical or within-study level. To foster easy adoption, all input can be entered through the MATLAB GUI; no coding skills are required. Apart from user-friendly automatization and minor features, ACES incorporates three principal methodological advancements. First, ACES allows to weight studies for meta-analytical purposes. Second, ACES incorporates a cluster-based method [5] which can handle the spatial contiguity that typically characterises |E|. This approach can retrieve small areas featuring strong associations between |E| and stimulation effect as well as large areas where they are only moderately associated. Third, the cluster-based permutation test implemented in ACES features adequate multiple comparison control. This is critical, given that, typically , tens of thousands of correlations are involved. A detailed practical manual and the algorithm itself can be found here: https://osf. io/5rswh/. Fig. 1 gives a general overview of the procedure. In a first step, ACES correlates |E| with a quantification of the stimulation effect, across studies or participants. This correlation is computed for each of the elements making up the SimNIBS output mesh. The results is a mesh with a correlation per element (performance-electric field correlation or PEC [3]). For example, a large PEC at a given site reflects that studies featuring higher intensity stimulation at that location tended to report larger effect sizes. As NIBS effects can be nonlinear [6], ACES supports both Pearson and Spearman's rank correlation, although Pearson might still be preferable in such circumstances [7]. The Spearman correlation is implemented as a Pearson correlation on value ranks with fractional ranking in case of ties. ACES uses the studentized correlation coefficient [8]. For meta-analytical purposes, the precision of individual studies may be important to consider, approximated by sample size, or through more advances weighting schemes. Therefore, ACES can weight studies equally, by sample size, or another precision measure, by means of the weighted Pearson correlation between variables x and y given study weights N: m(x; N) = ∑ i N i x i ∑ i N i cov(x, y; N) = ∑ i N i (x i m(x; N))(y i m(y; N)) ∑ i N i corr(x, y; N) = cov(x, y; N) ̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅ cov(x, x; N)cov(y, y; N) √ As |E| of neighbouring mesh elements differs only gradually, PECs of neighbouring mesh elements are not independent. Cluster-based permutation tests can handle significance testing in the context of such spatial correlation [5], identifying contiguous clusters of mesh elements with significant PECs. Thus, in a second step, an arbitrary threshold is used to filter out small correlations and demarcate clusters. Negative correlations are set to zero-if desired, negative correlations can be investigated by inverting the sign of the input effect sizes. Next, t-values of above-threshold PECs are summed for each contiguous cluster, to be used for significance testing. Finally, for the permutation test, effect sizes are shuffled and PECs recomputed, using the same thresholding and clustering procedure as on the observed true PECs. In case of weighting, the correspondence between effect sizes and sample sizes is maintained throughout the permutations. The maximal cluster score and maximal individual t-value across mesh elements is stored for each permutation. The position of observed (peak or cluster) values in the ordered list of the permuted values is used as a criterion for statistical significance, thus controlling for multiple comparisons [5,8]; e.g., 95th percentile corresponds to a one-sided α = 0.05. ACES outputs a table with cluster size, peak and cluster t and p, and 3D coordinates of cluster peaks. Analyses on surface meshes can be easily visualized, and we provide example code to automatize this procedure. While originally developed for meta-analytical purposes, the logic of ACES can be expanded to handle inter-subject variability at the within-study level. If individual anatomical data form participants are available , SimNIBS allows the user to first simulate fields in each uniqueThis work was supported by the Research Foundation Flanders (SVH, G1129923 N)
Neurophysiological and behavioral effects of oscillatory transcranial direct current stimulation (otDCS)
No full texthttp://dx.doi.org/10.13039/501100001655 German Academic Exchange Servicehttp://dx.doi.org/10.13039/501100004564 Republic of Serbia Ministry of Education Science and Technological Developmenthttp://dx.doi.org/10.13039/501100003246 Nederlandse Organisatie voor Wetenschappelijk Onderzoekhttp://dx.doi.org/10.13039/501100000780 European Commissionhttp://dx.doi.org/10.13039/501100001659 Deutsche Forschungsgemeinschafthttp://dx.doi.org/10.13039/501100002347 Bundesministerium für Forschung, Technologie und Raumfahrthttp://dx.doi.org/10.13039/100010661 Horizon 2020 Framework Programmehttp://dx.doi.org/10.13039/100018693 Horizon 202
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
Effects of 20 Hz transcranial alternating current stimulation on the frontal oscillations during reversal learning
No full textThe decisions we make are based on the feedback we receive. When actions are rewarded, they will be repeated, but if actions are punished, they will be avoided. Sometimes the environment we are surrounded by is changed, forcing us to adapt our behaviour to the new situation. Adapting one’s behaviour requires flexibility of the brain and this flexibility can be tested with reversal learning paradigms, where reward/punishment actions are changed during the task.
We used a probabilistic reversal learning task (80/20), where the rewards and punishments were switched twice during the task, while stimulating with 20 Hz transcranial alternating current stimulation (tACS) over the frontal cortex. Furthermore, resting state electroencephalography (EEG) was recorded immediately before and after the stimulation.
We aimed to establish the role of 20 Hz tACS on reversal learning, moreover whether it affects the speed by which one can learn a new rule, or if the rule implementation is affected. We further aimed to investigate the effect of tACS at 20 Hz on the frontal oscillating power bands.
Our results indicate that both inter-hemispheric in-phase and anti-phase 20 Hz tACS increase performance during reversal learning compared to a control condition. However, effects were larger and more consistent for the inter-hemispheric in-phase condition. The improved performance was driven by a better ability to apply the learned rule, rather than an increase in learning speed. No effects were found between the experimental conditions when comparing the pre-post levels of theta or beta activity, nor of the theta/beta ratio
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
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