1,721,018 research outputs found
Neuronale Grundlagen von Aufmerksamkeit
No full textPsychophysische Untersuchungen zur Rolle und Funktion von Aufmerksamkeit haben eine lange Tradition. ► Kap. 28 hat zu diesem Ansatz die wichtigsten Ergebnisse und die darauf fußenden Modelle vorgestellt. Dabei ist klar geworden, dass Aufmerksamkeit die Verarbeitung sensorischer Informationen beeinflusst, also wahrscheinlich die Aktivität sensorischer Neurone in der Großhirnrinde moduliert. Um zu verstehen, wie Aufmerksamkeit in die Aktivität von Neuronen eingreift, braucht es direktere Methoden als die Psychophysik. Es sind vor allem zwei Techniken, nämlich die Messung der Aktivität einzelner Neurone im Kortex wacher Tiere und von funktionellen Arealen im menschlichen Kortex, die sich in den letzten Jahren zu den bevorzugten Ansätzen bei der Suche nach den neuronalen Grundlagen von Aufmerksamkeit entwickelt haben
Absence of a common functional denominator of visual disturbances in cerebellar disease
No full textSeveral studies have demonstrated disturbances of visual perception in patients suffering from cerebellar disease. In an attempt to determine the cause of these visual disturbances and thereby the cerebellar contribution to vision, we designed two sets of experiments in which we tested (i) the possibility of a general magnocellular deficit in cerebellar disease and (ii) the alternative possibility of impaired spatial attention underlying visual disturbances in cerebellar patients. The first set of experiments consisted of a test of position discrimination, a parvocellular function and tests tapping different aspects of motion perception including speed discrimination, direction discrimination and the ability to extract a coherent motion signal embedded in noise. The second set of experiments compared the performance on two different classes of texture discrimination. The first one required fast and precise shifts of focal spatial attention ('serial search'), the second one, testing preattentive texture discrimination ('pop-out'), did not. In the first set of experiments cerebellar patients were impaired on the position discrimination task as well as several, albeit not all, tests of motion perception. The pattern of disturbances obtained was neither compatible with the notion of a selective magnocellular deficit nor the idea, originally put forward by Ivry and Diener (J Cogn Neurosci 1991; 3: 355–66) that visual deficits are secondary to an impaired measurement of time. In the second set of experiments, cerebellar patients showed normal performance on pop-out tasks and normal performance on all variants of the serial search task except for the one requiring comparison of a single element presented with a sample of the target in short-term memory. In summary, our results support the existence of visual disturbances in cerebellar disease, but provide evidence against a common, simple denominator such as a timing deficit, deficient cerebellar modulation of magnocellular circuitry, deficits of spatial attention or visual working memory
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
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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
Funktionelle Kernspinresonanztomografie sich aufmerksam verhaltender Affen
No full textBlood-oxygen-level-dependent (BOLD) functional Magnetic Resonance Imaging (fMRI) performed on a conventional 3 T MR scanner was used in order to investigate brain activity in response to visual stimuli and eye movements of an alert, behaving rhesus monkey.
The current study presents functional data on representations of meridians and different degrees of eccentricity of the visual field, on optic flow and on saccade and smooth pursuit eye movements (SPEMs).
A number of technical constraints - such as distortions of functional MR images - hampered the exact localization and identification of sites showing BOLD responses. Despite these limitations, the present results are largely in agreement with both the classical literature on monkey brain functions and comparable monkey fMRI studies.
Results of the present study are in accordance with the view that processing of optic flow requires cortical areas MT/MST (middle temporal/medial superior temporal). Furthermore, the present study implicates cortical areas that are well-known for their role in oculomotor function in the processing of saccadic eye movements and SPEMs, including area LIP (lateral intraparietal), as well as the FEF (frontal eye fields) and, albeit only weakly, the SEF (supplementary eye fields).
Future experiments will have to improve used material as well as experimental procedures in order to reduce artefacts in functional images. It will be of particular importance to reduce contributions of those artefacts that emerge from body movements of the monkey. Additional subjects will have to be tested in order to account for inter-individual effects.Mithilfe von Blutsauerstoff-abhängiger (BOLD) funktioneller Magnetresonanz-Tomographie (fMRT) wurde die Hirnaktivität als Antwort auf visuelle Stimuli und Augenbewegungen eines wachen, sich definiert verhaltenden Rhesus-Affens an einem konventionellen 3 T MR-Scanner untersucht.
Es werden funktionelle Daten zur Repräsentation von Meridianen und verschiedenen Exzentrizitäten des visuellen Feldes, zu optischen Flußfeldern, zu Sakkaden und zu glatten Augefolgebewegungen präsentiert.
Eine Reihe von technischen Schwierigkeiten - wie z.B. Verzerrungen von funktionalen MR-Bildern - erschwerten die exakte Ortsbestimmung und Identifikation derjenigen Hirngebiete, welche BOLD-Antworten zeigten. Ungeachtet dieser Limitationen sind die Ergebnisse dieser Studie jedoch weitgehend in Übereinstimmung, sowohl mit Ergebnissen der klassischen Literatur über Hirnfunktionen von Affen, als auch mit vergleichbaren fMRT-Studien an Affen.
Die Ergebnisse der vorliegenden Studie stimmen mit der Annahme überein, dass die Verarbeitung optischer Flußfelder die kortikalen Areale MT/MST (middle temporal/medial superior temporal) benötigt. Weiterhin implizieren die Ergebnisse dieser Studie kortikale Areale in der Verarbeitung von Sakkaden und glatten Augefolgebewegungen, deren Rolle in okulomotorischen Funktionen bekannt ist, einschließlich des Areals LIP (lateral intraparietal), der FEF (frontale Augenfelder) sowie, wenn auch nur schwach, der SEF (supplementäre Augenfelder).
Für zukünftige Experimente wird es erforderlich sein, das verwendete Material und die experimentellen Prozeduren zu verbessern, um Artefakte in den funktionellen Bildern zu reduzieren. Eine besondere Bedeutung wird dabei die Vermeidung von Artefakten spielen, die durch Körperbewegungen des Affen hervorgerufen werden. Weitere Affen werden untersucht werden müssen, um inter-individuellen Unterschieden gerecht zu werden
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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