1,721,038 research outputs found
Predicting Antidepressant Treatment Response From Cortical Structure on MRI : A Mega‐Analysis From the ENIGMA ‐ MDD Working Group
No full textABSTRACT Accurately predicting individual antidepressant treatment response could expedite the lengthy trial‐and‐error process of finding an effective treatment for major depressive disorder (MDD). We tested and compared machine learning‐based methods that predict individual‐level pharmacotherapeutic treatment response using cortical morphometry from multisite longitudinal cohorts. We conducted an international analysis of pooled data from six sites of the ENIGMA‐MDD consortium ( n = 262 MDD patients; age = 36.5 ± 15.3 years; 154 (59%) female; mean response rate = 57%). Treatment response was defined as a ≥ 50% reduction in symptom severity score after 4–12 weeks post‐initiation of antidepressant treatment. Structural MRI was acquired before, or < 14 days after, treatment initiation. The cortex was parcellated using FreeSurfer, from which cortical thickness and surface area were measured. We tested several machine learning pipeline configurations, which varied in (i) the way we presented the cortical data (i.e., average values per region of interest, as a vector containing voxel‐wise cortical thickness and surface area measures, and as cortical thickness and surface area projections), (ii) whether we included clinical data, and the (iii) machine learning model (i.e., gradient boosting, support vector machine, and neural network classifiers) and (iv) cross‐validation methods (i.e., k‐fold and leave‐one‐site‐out) we used. First, we tested if the overall predictive performance of the pipelines was better than chance, with a corrected 10‐fold cross‐validation permutation test. Second, we compared if some machine learning pipeline configurations outperformed others. In an exploratory analysis, we repeated our first analysis in three subpopulations, namely patients (i) from a single site, (ii) with comparable response rates, and (iii) showing the least (first quartile) and the most (fourth quartile) treatment response, which we call the extreme (non‐)responders subpopulation. Finally, we explored the effect of including subcortical volumetric data on model performance. Overall, performance predicting antidepressant treatment response was not significantly better than chance (balanced accuracy = 50.5%; p = 0.66) and did not vary with alternative pipeline configurations. Exploratory analyses revealed that performance across models was only significantly better than chance in the extreme (non‐)responders subpopulation (balanced accuracy = 63.9%, p = 0.001). Including subcortical data did not alter the observed model performance. Cortical structural MRI alone could not reliably predict individual pharmacotherapeutic treatment response in MDD. None of the used machine learning pipeline configurations outperformed the others. In exploratory analyses, we found that predicting response in the extreme (non‐)responders subpopulation was feasible on both cortical data alone and combined with subcortical data, which suggests that specific MDD subpopulations may exhibit response‐related patterns in structural data. Future work may use multimodal data to predict treatment response in MDD.Ministero della Salute https://doi.org/10.13039/501100003196Japan Agency for Medical Research and Development https://doi.org/10.13039/100009619Eurostars https://doi.org/10.13039/100013297Nederlandse Organisatie voor Wetenschappelijk Onderzoek https://doi.org/10.13039/501100003246National Institute of Mental Health https://doi.org/10.13039/100000025National Health and Medical Research Council https://doi.org/10.13039/501100000925Bundesministerium für Bildung und Forschung https://doi.org/10.13039/50110000234
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
Acute stress effects on prefrontal cortex GABA and glutamate concentrations, and their correlations to electrocardiographic markers
No full textBachelorarbeit - Veterinärmedizinische Universität Wien - 2020Die Stressantwort im Menschen ist eine systemische Anstrengung der Erhaltung homöostatischen Gleichgewichts unter realer, wahrgenommener oder antizipierter Gefahr. In der Peripherie wird sie durch das autonome Nervensystem (ANS) und durch zirkulierendes Cortisol, dem Endprodukt der Hypothalamus-Hypophysen-Nebennierenrinden-Achse (HPA), vermittelt. Das zentrale Nervensystem übernimmt hierbei die Regulation der Intensität und Dauer der peripheren Reaktion und integriert zudem Stresssignale in kognitive Prozesse und das Verhalten. Eine Maladaption dieses komplexen Systems (etwa durch chronische oder überintensive Belastung) kann verheerende Auswirkungen auf geistige und körperliche Gesundheit - einschließlich der des Herzens - haben. So wurden stresslastige Lebensperioden mit Herzrhythmusstörungen in Verbindung gebracht und können in seltenen Fällen zu plötzlichem Herztod (SCD) führen, möglicherweise wegen einer Störung ANS-bedingter Regulationsmechanismen.Die Bedeutung präfronto-limbischer Strukturen wie dem dorsalen cortex cingularis anterior (dACC) und -Aminobuttersäure-(GABA)-erger Neuronen in der Stressregulation ist weit anerkannt. GABA-Rezeptor-Antagonisten wie Bicucullin werden als anxiogen eingestuft, während GABA-Rezeptor-agonistische Medikamente, wie etwa Mitglieder der Benzodiazepin-Familie, üblicherweise für ihre anxiolytische Wirkung verschrieben werden. In Übereinstimmung mit diesen Erkenntnissen hat eine Magnetresonanzspektroskopie-Studie (MRS) bereits gezeigt, dass die präfrontalen GABA-Konzentrationen in unmittelbarer Reaktion auf Stress abnehmen. Darüber hinaus bestätigen neuere Berichte, dass ein plötzliches Absetzen GABA-Rezeptor-agonistischer Medikamente zur Entwicklung einer Kardiomyopathie führen kann, die klinisch von SCD nicht zu unterscheiden ist.Mit diesem Hintergrund wurde in der vorliegenden Studie der Zusammenhang präfrontaler GABA-Konzentrationen und Herzparametern untersucht. Hierfür wurden 56 psychisch und physisch gesunde Männer (Durchschnittsalter = 24,18 Jahre) einem gängigen Stressparadigma (dem Socially Evaluated Cold Pressor Task) unterzogen, und anschließend mittels 7T MRS deren GABA- und Glutamatgehalt im dACC gemessen. Wir bedienten uns einer semi-localiza-tion by adiabatic selective refocusing (sLASER) Messsequenz (TR / TE = 3600/36 ms), wobei64 Spektra vor, und 368 Spektra nach der Stressintervention in einem aufgabennegativen Umfeld aufgenommen wurden. Zusätzlich wurden Cortisolgehalt im Speichel und elektrokardio- graphische (ECG) Marker der Teilnehmer ermittelt, um das Ausmaß einer HPA- bzw. ANS- Aktivierung zu bestimmen. Spektroskopie- und ECG-Daten wurden im selben Kontext analysiert, um die Möglichkeit zeitlicher Abhängigkeiten zu untersuchen, und um diese als Parameter für die Stressempfindlichkeit zu evaluieren. Wir stellten wider anfänglicher Annahme keine Unterschiede zwischen Stress- und Kontrollgruppe in Hinblick präfrontaler GABA-Konzentrationen fest, jedoch hatten wir in dieser Analyse mit kritischen Datenverlusten umzugehen. Die verringerte Aussagekraft unsere Auswertung könnte kleine Effekte außer Acht lassen, eine Validierung unserer Ergebnisse mit funktioneller Magnetresonanz-Datensätze ist im nächsten Schritt daher von besonderer Bedeutung. Wir zeichneten ebenfalls keinen Effekt von Stress auf ECG-Parameter auf, und wir hinterfragen die Eignung dieser zur Messung von SAM-Aktivierung in dem vorliegenden experimentellen Kontext. Aufgrund zeitlicher Einschränkungen war der Cortisol-Datensatz nicht Teil der Analyse; HPA- und SAM-Aktivität müssen zu einem späteren Zeitpunkt nochmals eruiert werden.Bachelor thesis - University of Veterinary Medicine Vienna - 2020The human stress response is a systemic effort to maintain homeostatic balance under real, perceived, or anticipated threat. In the periphery, its effects are mediated by the autonomic nervous system (ANS) and bloodstream cortisol, end product of the hypothalamus-pituitary- adrenocortical axis (HPA). All is overseen by a central nervous regulatory component, which adjusts the intensity and duration of peripheral response and integrates peripheral signals of stress into higher-order cognitive and behavioral processes. A dysregulation of this complex system (through prolonged or over-intensive exposure to stress) can have devastating effects on mental and physical health, including cardiac health. For example, periods of severe acute stress have been linked to cardiac arrythmias and can even lead to sudden cardiac death (SCD), possibly due to a disruption in ANS control of the heart. The importance of prefronto-limbic structures such as the dorsal anterior cingulate cortex (dACC) and aminobutyric acid (GABA) pathways in stress regulation is widely recognized. GABA-receptor antagonists such as bicuculline are categorized as anxiogenic, whereas GABA- receptor agonistic medication such as members of the benzodiazepine family are commonly prescribed for their anxiolytic effects. Consistent with these insights, a previous magnetic resonance spectroscopy (MRS) study has shown prefrontal GABA concentrations to decrease in immediate response to stress. Moreover, recent reports confirm sudden discontinuation of GABA-receptor agonistic medication can result in development of cardiomyopathy clinically indistinguishable from SCD. The present study extends this research by investigating possible correlates between prefrontal GABA concentrations and cardiac markers. Fifty-six psychologically and physically healthy males (mean age = 24.18) were included in a between-subject experimental setup to investigate GABA and glutamate response in the dACC to a well-established stress task (i.e. the Socially Evaluated Cold Pressor Task). We adopted a semi-localization by adiabatic selective refocusing (sLASER) measuring sequence (TR/TE = 3600/36 ms) at ultra-high field 7T MRS, acquiring 64 spectra before, and 368 spectra after the stress intervention in a task-negative setting. Additionally, salivary cortisol content and electrocardiographic (ECG) markers of participants were measured to determine HPA and ANS activation, respectively. Spectroscopy and ECG data was analyzed in the same context to explore the possibility of temporal dependencies between the two and assessed for reliable measures of stress vulnerability. We did make out a significant difference between stress and control group in terms of dACC GABA modulation. This goes against the notion that GABA is a key regulator in the stress response, however, data loss was a critical issue in this analysis. Reduced statistical power might leave small effects unnoticed and as a next step we will validate our findings with functional magnetic resonance imaging datasets. Furthermore, we found the stress task to have no effect on ECG parameters, and we raise the question of its suitability to measure SAM activation in the paradigm at hand. Due to timely restrictions, salivary cortisol data could not be included in the analysis; HPA and SAM activation will have to be addressed at a later point again
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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