1,721,012 research outputs found
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
Using flicker light stimulation to unravel distinct changes in thalamocortical connectivity associated with visual hallucinatory experiences
Full text linkBright, full-field flicker light stimulation (FLS) has long been known to induce colourful and geometric visual hallucinations in humans. However, the underlying neural mechanisms of flicker-induced visual hallucinations (FI-VHs) are still largely unknown. Since human fMRI studies have found that increased thalamocortical connectivity is associated with visual hallucinations in various psychopathologies and following pharmacological intervention (e.g., via serotonergic psychedelics), it poses the open question of whether thalamocortical interactions also contribute to FI-VHs. Moreover, to develop a better understanding of the role of thalamocortical interactions within visual hallucinatory experiences, it is important to consider that the thalamus contains multiple functionally distinct nuclei. Therefore, assessing which thalamic nuclei exhibit changes in connectivity during FI-VHs could help to unravel the corresponding functional contributions of thalamocortical connectivity within visual hallucinations. Furthermore, as FLS elicits fewer physiological confounds than psychopathology and pharmacological intervention, identifying the distinct thalamocortical connectivity changes during FI-VHs could inform the overarching mechanisms of visual hallucinatory experiences.
Therefore, this work investigates changes in thalamocortical connectivity with distinct thalamic nuclei during hallucination-inducing FLS. The first study aims to characterise the prevalent pattern types reported during FI-VHs and assesses the stimulation parameters (i.e., flicker frequency and rhythmicity) that affect the subjective intensity of FI-VHs. Thereafter, using resting-state fMRI, flicker frequency- and rhythmicity-dependent changes in thalamocortical connectivity are tested. Here, it is revealed that rhythmic FLS at 10 Hz, i.e. the FLS condition that elicits the most intense FI-VHs, selectively increases connectivity between ventroanterior thalamic nuclei and higher-order visual cortices compared to control conditions.
Ventroanterior thalamic nuclei are higher-order nuclei, making it likely that the role of increased thalamocortical connectivity within visual hallucinations relates to a higher-order function of the thalamus, such as modulating the excitability of cortical neurons. This aligns with the functions of thalamocortical interactions proposed by dendritic integration theory. Future work should test whether these findings also apply to visual hallucinations during psychopathology and pharmacological interventions.Es ist seit langem bekannt, dass helle, flimmernde Lichtstimulation (FLS) beim Menschen farbige und geometrische visuelle Halluzinationen hervorruft. Die zugrundeliegenden neuronalen Mechanismen der flimmerinduzierten visuellen Halluzinationen (FI-VHs) sind jedoch noch weitgehend unbekannt. Da fMRT-Studien am Menschen ergeben haben, dass eine erhöhte thalamokortikale Konnektivität mit visuellen Halluzinationen bei verschiedenen Psychopathologien und nach pharmakologischen Eingriffen (z. B. durch serotonerge Psychedelika) einhergeht, stellt sich die offene Frage, ob thalamokortikale Interaktionen auch zu FI-VHs beitragen. Um ein besseres Verständnis der Rolle thalamokortikaler Interaktionen bei visuellen Halluzinationen zu entwickeln, ist es außerdem wichtig zu berücksichtigen, dass der Thalamus mehrere funktionell unterschiedliche Kerne enthält. Daher könnte die Untersuchung der Thalamuskerne, die während FI-VHs Veränderungen in der Konnektivität aufweisen, dazu beitragen, die entsprechenden funktionellen Beiträge der thalamokortikalen Konnektivität bei visuellen Halluzinationen zu entschlüsseln. Da FLS weniger physiologische Störungen hervorruft als Psychopathologie und pharmakologische Interventionen, könnte die Identifizierung der ausgeprägten thalamokortikalen Konnektivitätsveränderungen während FI-VHs zudem Aufschluss über die übergreifenden Mechanismen visueller halluzinatorischer Erfahrungen geben.
Daher werden in dieser Arbeit Veränderungen in der thalamokortikalen Konnektivität mit verschiedenen Thalamuskernen während Halluzinationen auslösender FLS untersucht. Die erste Studie zielt darauf ab, die vorherrschenden Mustertypen, die während FI-VHs berichtet werden, zu charakterisieren und die Stimulationsparameter (d.h. Flimmerfrequenz und Rhythmik) zu bewerten, die die subjektive Intensität von FI-VHs beeinflussen. Anschließend werden mittels fMRI im Ruhezustand flimmerfrequenz- und rhythmusabhängige Veränderungen der thalamokortikalen Konnektivität untersucht. Hier zeigt sich, dass rhythmisches FLS bei 10 Hz, d.h. die FLS-Bedingung, die die intensivsten FI-VHs hervorruft, selektiv die Konnektivität zwischen ventroanterioren thalamischen Kernen und visuellen Kortizes höherer Ordnung im Vergleich zu Kontrollbedingungen erhöht.
Ventroanteriore Thalamuskerne sind Kerne höherer Ordnung, so dass es wahrscheinlich ist, dass die Rolle der erhöhten thalamokortikalen Konnektivität bei visuellen Halluzinationen mit einer Funktion höherer Ordnung des Thalamus zusammenhängt, wie z. B. der Modulation der Erregbarkeit kortikaler Neuronen. Dies stimmt mit den Funktionen thalamokortikaler Interaktionen überein, die von der Theorie der dendritischen Integration vorgeschlagen werden. In künftigen Arbeiten sollte geprüft werden, ob diese Erkenntnisse auch für visuelle Halluzinationen bei Psychopathologie und pharmakologischen Interventionen gelten
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
The effect of long-duration spaceflight on brain structure and function
No full textAbstract: In over half a century of crewed missions to space, many different effects of spaceflight on the human body have been uncovered so far. However, little focus has been directed to investigating how space stressors affect the human brain. The largest body of work in this dissertation describes pioneering findings on brain structural and functional changes after spaceflight in Roscosmos cosmonauts by means of multi-modal magnetic resonance imaging (MRI) in a longitudinal and prospective design. Structural MRI modalities, such as T1-weighted and diffusion MRI, were used to unravel macroscopic volume and microstructural brain tissue composition changes. We found a widespread redistribution of the cerebrospinal fluid (CSF) with secondary mechanistic effects on the grey matter (GM) tissue. We also revealed increased neural tissue volume in motor regions of the brain that suggest evidence for structural brain adaptations, also known as neuroplasticity, associated with altered motor strategies in space. Most CSF changes after spaceflight were still detectable more than half a year after return to Earth, while the GM changes after spaceflight partially reversed in the long term. In addition, functional MRI data was acquired in these cosmonauts to study functional reorganisation of the brain after spaceflight, showing numerous functional connectivity (FC) alterations after spaceflight. Some of these changes persisted in the longer-term, whereas other changes returned back to pre-flight levels. Furthermore, this work also describes the experimental work and preliminary analyses of several Earth-based models. One is a longitudinal MRI pilot study in hindlimb-unloaded (HLU) mice, inducing fluid shifts to the head region, in order to better understand the consequence of these fluid shifts on the brain. A second study was performed in fighter pilots as a model for exposure to high g-levels and sensory conflicts, in which FC was compared to that in a control group. This work rendered a vast increase in available information on structural and functional brain changes after spaceflight compared to several years ago. In the future, the underlying mechanisms of the observed findings need to be understood in more detail. Ultimately, we aim to characterise the effects space stressors have on the brain, to then attempt to mitigate these changes through countermeasures and characterise beneficial coping mechanisms that we can enhance, in order to be fully prepared for future exploration missions into deep space
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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