1,720,974 research outputs found
Beyond the surface: how ex-vivo diffusion-weighted imaging reveals large animal brain microstructure and connectivity
Get PDFDiffusion-weighted Imaging (DWI) is an effective and state-of-the-art neuroimaging method that non-invasively reveals the microstructure and connectivity of tissues. Recently, novel applications of the DWI technique in studying large brains through ex-vivo imaging enabled researchers to gain insights into the complex neural architecture in different species such as those of Perissodactyla (e.g., horses and rhinos), Artiodactyla (e.g., bovids, swines, and cetaceans), and Carnivora (e.g., felids, canids, and pinnipeds). Classical in-vivo tract-tracing methods are usually considered unsuitable for ethical and practical reasons, in large animals or protected species. Ex-vivo DWI-based tractography offers the chance to examine the microstructure and connectivity of formalin-fixed tissues with scan times and precision that is not feasible in-vivo. This paper explores DWI’s application to ex-vivo brains of large animals, highlighting the unique insights it offers into the structure of sometimes phylogenetically different neural networks, the connectivity of white matter tracts, and comparative evolutionary adaptations. Here, we also summarize the challenges, concerns, and perspectives of ex-vivo DWI that will shape the future of the field in large brains
functional MRI data of actively discriminating pigeons
No full textUntil now, only fMRI studies with humans and non-human primates employed paradigms in which subjects had to actively respond to a stimulus. This extreme restriction on the side of model species implies that fMRI-based insights on most perceptual and cognitive tasks essentially stem from two closely related species of which macaques are difficult and expensive to house as well as laborious to train. The most important scientific problem of this restriction is, however, the difficulty to transfer results to most other vertebrates, especially very distantly related ones like birds. We established an fMRI paradigm in which awake pigeons discriminated in a Go/NoGo paradigm to upcoming stimuli with a beak movement to signal their acceptance or rejection of the stimulus. This dataset contains fMRI and anatomical scans during color discrimination experiment and fMRI time-series for HRF estimation. During color discrimination, pigeons were involved in a Go/NoGo paradigm. The dataset can be used to assess the activated brain networks during color discrimination. It also allows for the investigation of inhibitory networks.
More details can be found in the related publication: Behroozi M., Helluy X., Ströckens F., Meng G., Pusch R., Tabrik S., Tegenthoff M., Otto T., Axmacher N., Kumsta R., Moser D., Genc E., and Güntürkün O. Event-Related functional MRI in awake behaving pigeons.(2020
functional MRI data of actively discriminating pigeons
No full textUntil now, only fMRI studies with humans and non-human primates employed paradigms in which subjects had to actively respond to a stimulus. This extreme restriction on the side of model species implies that fMRI-based insights on most perceptual and cognitive tasks essentially stem from two closely related species of which macaques are difficult and expensive to house as well as laborious to train. The most important scientific problem of this restriction is, however, the difficulty to transfer results to most other vertebrates, especially very distantly related ones like birds. We established an fMRI paradigm in which awake pigeons discriminated in a Go/NoGo paradigm to upcoming stimuli with a beak movement to signal their acceptance or rejection of the stimulus. This dataset contains fMRI and anatomical scans during color discrimination experiment and fMRI time-series for HRF estimation. During color discrimination, pigeons were involved in a Go/NoGo paradigm. The dataset can be used to assess the activated brain networks during color discrimination. It also allows for the investigation of inhibitory networks.
More details can be found in the related publication: Behroozi M., Helluy X., Ströckens F., Meng G., Pusch R., Tabrik S., Tegenthoff M., Otto T., Axmacher N., Kumsta R., Moser D., Genc E., and Güntürkün O. Event-Related functional MRI in awake behaving pigeons.(2020
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
Constrained spherical deconvolution on diffusion-weighted images of dolphin brains
Get PDFInvasive neuronal tract-tracing is not permitted in very large or endangered animals. This is especially the case in marine mammals like dolphins. Diffusion-weighted imaging of fiber tracts could be an alternative if feasible even in brains that have been fixed in formalin for a long time. This currently is a problem, especially for detecting crossing fibers. We applied a state-of-the-art algorithm of Diffusion-weighted imaging called Constrained Spherical Deconvolution on diffusion data of three fixed brains of bottlenose dolphins using clinical human MRI parameters and were able to identify complex fiber patterns within a voxel. Our findings indicate that in order to maintain the structural integrity of the tissue, short-term post-mortem fixation is necessary. Furthermore, preprocessing steps are essential to remove the classical Diffusion-weighted imaging artifacts from images: however, the algorithm is still able to resolve fiber tracking in regions with various signal intensities. The described imaging technique reveals complex fiber patterns in cetacean brains that have been preserved in formalin for extended periods of time and thus opens a new window into our understanding of cetacean neuroanatomy
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