1,720,955 research outputs found
Brain-wide microstrokes affect the stability of memory circuits in the hippocampus
No full textCognitive deficits affect over 70% of stroke survivors, yet the mechanisms by which multiple small ischemic events contribute to cognitive decline remain poorly understood. In this study, we employed chronic two-photon calcium imaging to longitudinally track the fate of individual neurons in the hippocampus of mice navigating a virtual reality environment, both before and after inducing brain-wide microstrokes. Our findings reveal that, under normal conditions, hippocampal neurons exhibit varying degrees of stability in their spatial memory coding. However, microstrokes disrupted this functional network architecture, leading to cognitive impairments. Notably, the preservation of stable coding place cells, along with the stability, precision, and persistence of the hippocampal network, was strongly predictive of cognitive outcomes. Mice with more synchronously active place cells near important locations demonstrated recovery from cognitive impairment. This study uncovers critical cellular responses and network alterations following brain injury, providing a foundation for novel therapeutic strategies preventing cognitive decline
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
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
Two-Photon Imaging of Distributed Neural Activity in Mouse Cortex During Multisensory Processing
Full text linkThe brain consists of distributed networks of cells which allow us to perceive the world and act in it. For individual neurons, this distributed nature of brain circuits poses a challenge. During multisensory integration, for example, sensory signals from different sensory modalities converge on individual neurons and need to be combined. Additionally, the transformations of these inputs might vary with the state of other networks in the brain. Two projects in this thesis address the role of individual neurons in distributed networks in the mouse brain. In the first project, the integration of visual and tactile sensory information about a nearby object was investigated in the posterior parietal cortex. In the second project, a method to combine cortical two-photon calcium imaging with subcortical flexible electrode recordings was established to investigate thalamo-cortical coupling. The first chapter introduces the brain structures that process visual, tactile, and multisensory sensory stimuli. The chapter describes the processing steps that lead to sensory representations of a nearby object in the visual and somatosensory processing pathways. This overview is followed by a description of the role of the posterior parietal cortex to merge these representations. In addition, optical and electrical single-cell recording techniques and their potential combinations are introduced. The second chapter describes the methods used to investigate multisensory processing. For the work of this thesis, neural activity in layer 2/3 of the posterior cortex of head-fixed mice was recorded with two-photon calcium imaging. At the same time, mice could touch and see a vertical pole that was presented at different rostro-caudal locations. To combine electrical and optical recordings, a 64-channel flexible electrode was implanted into the thalamus together with a cranial window over the posterior cortex. The third chapter presents the results of both projects. We found that subsets of neurons in the mouse barrel cortex (SSp-bfd), visual cortex (VISp), and posterior parietal cortex (VISrl, VISa) showed selectivity for specific locations in the near space. In the posterior parietal cortex, location selectivity was driven by both visual and tactile signals and cells were organized along a shared spatial gradient. Multisensory responses occurred in a subset of posterior parietal cortex neurons, with more neurons reducing compared to increasing their activity at touch onsets during illumination. To investigate thalamo-cortical coupling, we established a chronic preparation to simultaneously record electrical signals from the thalamus and optical signals from the cortex of awake mice. We demonstrated the long-term stability of the flexible electrode recordings and the feasibility of simultaneous two-photon imaging. Using this method, we identified groups of cortical neurons that were differentially correlated to thalamic activity based on the behavioral state of the mouse. The fourth chapter discusses these results in the context of the current literature and provides an outlook. Our findings highlight the role of the mouse posterior parietal cortex as a hub to integrate visual and tactile sensory signals and suggest the presence of a visual-tactile map of the nearby space in the posterior parietal cortex. This visual-tactile integration could serve as a paradigm to study the principles of coordinate transformations required in cortico-cortical communication during multisensory processing. Our simultaneous electrical and optical recordings demonstrated a method to record neural population activity throughout the brain. In the future, similar uses of combined methods might provide further insights in the role of individual neurons in distributed networks
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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