1,721,005 research outputs found
Influences of negative BOLD responses on positive BOLD responses
No full textUnderstanding possible interactions between blood oxygenation level-dependent (BOLD) responses is critical for model-based analyses and the interpretation of experiments that deal with stimuli presented close together in time. Such interactions are well documented in the case of successive positive BOLD responses. However, the influence that a stimulus-induced, negative BOLD response exerts on a subsequent positive BOLD response has yet to be investigated and is the focus of the current study. We performed functional magnetic resonance imaging on 10 healthy subjects during bilateral electrical median nerve stimulation using five different time intervals between left- and right-sided stimuli. We found an acute interruption of the ongoing negative BOLD response at the onset of the positive BOLD response. Different parameters characterizing the positive BOLD response were estimated. There was no impact of the preceding negative BOLD response on the parameters describing the subsequent positive BOLD response. These findings indicate that the underlying mechanisms for negative and positive BOLD responses do not engage parallel processes. We hypothesize that the negative BOLD response is caused by a decreased release of the same vasodilatative agents that evoke the positive BOLD response. Additionally, our results demonstrate that there is no need to adjust the model of a positive BOLD response due to a preceding negative BOLD response in the same brain area. (C) 2011 Elsevier Inc. All rights reserved
Functional Deactivations: Multiple Ipsilateral Brain Areas Engaged in the Processing of Somatosensory Information
No full textSomatosensory signals modulate activity throughout a widespread network in both of the brain hemispheres: the contralateral as well as the ipsilateral side of the brain relative to the stimulated limb. To analyze the ipsilateral somatosensory brain areas that are engaged during limb stimulation, we performed functional magnetic resonance imaging (fMRI) in 12 healthy subjects during electrical median nerve stimulation using both a block-and an event-related fMRI design. Data were analyzed through the use of model-dependent (SPM) and model-independent (ICA) approaches. Beyond the well-known positive blood oxygenation level-dependent (BOLD) responses, negative deflections of the BOLD response were found consistently in several ipsilateral brain areas, including the primary somatosensory cortex, the supplementary motor area, the insula, the dorsal part of the posterior cingulate cortex, and the contralateral cerebellum. Compared to their positive counterparts, the negative hemodynamic responses showed a different time course, with an onset time delay of 2.4 s and a peak delay of 0.7 s. This characteristic delay was observed in all investigated areas and verified by a second (purely tactile) event-related paradigm, suggesting a systematic difference for brain areas involved in the processing of somatosensory information. These findings may indicate that the physiological basis of these deactivations differs from that of the positive BOLD responses. Therefore, an altered model for the negative BOLD response may be beneficial to further model-dependent fMRI analyses. Hum Brain Mapp 32: 127-140, 2011. (C) 2010 Wiley-Liss, Inc
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Research Data Management and Data Sharing for Reproducible Research-Results of a Community Survey of the German National Research Data Infrastructure Initiative Neuroscience
Get PDFScience is changing: the volume and complexity of data are increasing, the number of studies is growing and the goal of achieving reproducible results requires new solutions for scientific data management. In the field of neuroscience, the German National Research Data Infrastructure (NFDI-Neuro) initiative aims to develop sustainable solutions for research data management (RDM). To obtain an understanding of the present RDM situation in the neuroscience community, NFDI-Neuro conducted a comprehensive survey among the neuroscience community. Here, we report and analyze the results of the survey. We focused the survey and our analysis on current needs, challenges, and opinions about RDM. The German neuroscience community perceives barriers with respect to RDM and data sharing mainly linked to (1) lack of data and metadata standards, (2) lack of community adopted provenance tracking methods, (3) lack of secure and privacy preserving research infrastructure for sensitive data, (4) lack of RDM literacy, and (5) lack of resources (time, personnel, money) for proper RDM. However, an overwhelming majority of community members (91%) indicated that they would be willing to share their data with other researchers and are interested to increase their RDM skills. Taking advantage of this willingness and overcoming the existing barriers requires the systematic development of standards, tools, and infrastructure, the provision of training, education, and support, as well as additional resources for RDM to the research community and a constant dialogue with relevant stakeholders including policy makers to leverage of a culture change through adapted incentivization and regulation
Variations on the Author
Get PDF“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
Get PDFWe 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
Volumenänderung der mimischen Muskulatur in Magnetresonanztomografie-Aufnahmen bei Patienten mit Fazialisparese unter transkutaner Elektrostimulation
Get PDFIn der Beobachtungsstudie wurde die Volumenänderung mimischer Muskulatur nach kompletter unilateraler peripherer Fazialisparese in MRT- Aufnahmen ermittelt und der Effekt von Elektrostimulation und Reinnervation auf das Muskelvolumen evaluiert. Dafür wurden von vier weiblichen und einem männlichen Patienten im Alter von 28 bis 59 Jahren mit kompletter peripherer Fazialisparese, vier bis sieben MRT-Datensätze in einem Zeitraum von sieben bis 15 Monaten zwischen erster und letzter MRT-Aufnahme erhoben. Die Patienten führten in dieser Zeit zweimal täglich dreimal fünf Minuten Elektrostimulation im Heimtraining durch. Mithilfe einer Bildbearbeitungssoftware wurden bestimmte Muskeln beider Gesichtshälften aus den MRT-Datensätzen segmentiert und die Veränderungen der Muskelvolumina über die Zeit ausgewertet. Es konnte gezeigt werden, dass die paretisch induzierte Atrophie der mimischen Muskulatur durch eine Elektrostimulation nicht verhindert werden kann. Ein einheitliches Muster der Volumenänderung durch die Elektrostimulation bei den fünf Patienten konnte nicht erkannt werden. Die Verläufe der Muskelvolumina über den Beobachtungszeitraum der fünf Patienten variierten deutlich. Es wurde gezeigt, dass erst mit Reinnervation die Muskelvolumina größer bzw. die Seitenunterschiede kleiner wurden. Es wurde eine historische Kontrollgruppe zum Vergleich herangezogen. Es konnte eine Atrophierate ohne den Einfluss einer Reinnervation und Elektrostimulation von -1,1 bzw. -3 % berechnet und ein statistisch signifikanter Unterschied im Vergleich zu den Patienten dieser Studie gezeigt werden. Somit konnte in dieser Arbeit dargestellt werden, dass Volumenänderungen der mimischen Muskulatur in MRT-Aufnahmen detektierbar sind und es einen positiven Effekt der Elektrostimulation und der Reinnervation auf das Volumen der segmentierten Muskeln gibt
Prognose der Erholung bei Patienten mit einer akuten peripheren Fazialisparese
Get PDFIn dieser Studie wurden prognostische Parameter für die Erholung nach einer akuten peripheren Fazialisparese (AFP) an 632 Patienten im UKJ untersucht. Die Ätiologie der AFP wurde in 7 Gruppen, Schweregrad mittels Grading-Systeme eingeteilt. Elektrodiagnostik und Topodiagnostik stellten zusätzliche Parameter für die Ausprägung der AFP dar. Im Mittelpunkt standen verschiedene Zeitintervalle, z.B. wann eine Therapie nach Paresebeginn begann. In der vorliegenden Arbeit zeigte sich die idiopathische Fazialisparese (IFP) mit 58,2 %, Ramsey-Hunt-Syndrom mit 15,2 % und postoperativ verursachte Fazialisparesen mit 10,6 %, restliche Ursachen traten <10 % auf. Ø 4 Tage nach Beginn der AFP wurde mit Diagnostik und Therapie begonnen. Die Zeitspanne bis zur ersten Feststellung einer Besserung lag bei ø 16 Tagen. Restitutio ad integrum erfuhren 48,6 % nach ø1,9 Monaten. Eine Borrelien ausgelöste FP zeigte beste Remissionschancen. Positiven Einfluss auf eine Remission hatten: Ätiologie, rascher Behandlungsbeginn, frühzeitige Symptomregredienz, Willküraktivität, fehlende pathologische Spontanaktivität im EMG, inkomplette Parese und unauffälliges Audiogramm. Positiven Einfluss auf eine Restitutio ad integrum hatten zusätzlich: unauffälliges ENG und Schirmertest, sowie vorhandener Stapediusreflex. Die multivariate Cox-Regressionsanalyse ermittelte die Ätiologien IFP als positiven, postoperative und sonstige FP als negative Prädiktoren auf eine Restitutio. Weitere unabhängige, positive Prädiktoren waren: Zeitabstand <4 Tagen bis Therapiebeginn und <16 Tagen bis Symptomregredienz, Stennert-Gesamtindex ≤6, unauffälliges ENG und vorhandener Stapediusreflex. Negativen Einfluss auf die Remissionszeit hatten pathologische Spontanaktivitäten im EMG. Zusammenfassend lässt sich festhalten, dass Stapediusreflexmessung, EMG und ENG bei Erstdiagnostik unerlässlich sind. Frühzeitiger medikamentöser Therapiebeginn und zeitnahe Symptomregredienz sind assoziiert zu einem besseren Heilungsverlauf
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