1,721,047 research outputs found
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Modeling physiological oscillations in a biologically constrained CA1 network from two perspectives: full-scale parallel network and rationally reduced Network Clamp
Full text linkI developed a full-scale, biologically constrained model of hippocampal CA1 subfield that is capable of spontaneous theta and gamma oscillations with distinct interneuronal phase preferences. In addition to structural constraints on the cell numbers and connectivity, experimental observations drove the development of the electrophysiology for the nine cell types and their synapses. To characterize and experimentally constrain the model, I designed and developed a custom software tool called SimTracker. SimTracker works with my NEURON code template to enable efficient coding, simulation design and execution, and analysis of results for parallel network NEURON simulations. I also created the Network Clamp, a software tool that implements the concept of a rational method for reducing a full-scale parallel network model to a small, yet biologically constrained model whose simulations can be run on a personal computer. Here I characterize the physiological oscillations displayed by the model. Additionally, I explore the parameter-space of the model by studying its oscillatory properties while manipulating its connectivity, excitation level, and synapse kinetics. This dual approach model is well characterized, flexible and accessible, and it represents a useful collation of experimental knowledge as well as a significant technical advance in neural network modeling
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Control of spatial memory and seizures by hippocampal mossy cells
Full text linkTemporal lobe epilepsy is the most common neurological disorder in adults and one of the most medically refractory. In order to develop new, more effective therapeutical approaches for TLE, we need a more complete understanding of the hippocampal structural and functional alterations underlying seizure activity and comorbid cognitive deficits. We investigated the contribution of two excitatory cell populations in the hippocampal dentate gyrus to ictal activity and spatial memory, the enigmatic hilar mossy cells and the granule cells, utilizing a combination of optogenetic, electrophysiological, and behavioral approaches in awake, behaving animals. Our main findings are: 1) decreased mossy cell activity during spontaneous, electrographic seizures permits further generalization of electrographic seizures into behavioral seizures; 2) mossy cells play a protective and anti-epileptic role in preventing seizure propagation; 3) mossy cells are necessary for encoding of spatial information, and a loss or decrease in mossy cell activity leads to memory impairments; 4) restoration of the dentate gyrus to a hyperpolarized state can robustly control seizure activity in chronic temporal lobe epilepsy, while stimulation of dentate gyrus granule cells leads to convulsive seizures. Our work has important implications for future therapeutical approaches. Our findings suggest that strategies to target the dentate gyrus microcircuitry, for example, by limiting MC loss, directly exciting surviving MCs, or inhibiting granule cells, may provide powerful treatment options for seizure control
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
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Computational Models of the Hippocampus in Radiation and Epilepsy
Full text linkComputational modeling of neuronal networks enables the study of variables in isolation while approximating the biological state. In conditions such as the exposure to radiation and epilepsy, a large number of structural and network parameters are altered, making the role of any individual abnormality unclear. The goal of the presented work is to develop realistic computational models of the hippocampus for the incorporation of experimental observations and to shed light on the relative importance and deleteriousness of pathological alterations. The Introduction summarizes our motivations and the utility of realistic computational models, particularly for the hippocampus, and gives a background for the abnormalities present in the irradiated and epileptic conditions. Chapter 1 describes our work translating our previous model to be compatible with parallel computing and then expanding the model to run at full-scale, with over a million neurons. It then outlines a methodology for the generation of computational models for the dendritic trees of granule cells, the most prevalent cell type in the dentate gyrus, using previous tools that contained a microscopic focus. In Chapter 2, we report an entirely new methodology for morphology generation that instead shifts the focus to the macroscopic neuroanatomy, growing dendrites within a realistic three-dimensional structure and enabling the population-level study of morphology. Chapter 3 describes a study in which our computational modeling was used to interpret experimental observations in area CA1 of the hippocampus after exposure to proton radiation. The study reports long-term but subtle changes in the passive properties of pyramidal neurons, the principal excitatory cell type in CA1, which were found in a computational model to have a surprisingly dramatic effect on network function. Chapter 4 reviews the ever-growing observations of the non-recurrent microscopic nature of seemingly repetitive macroscopic events in epilepsy. Chapter 5 provides the immediate next steps and future directions for computational modeling in health and disease, building on the foundation and framework provided in the previous chapters to suggest several avenues to bring computational models ever closer to the experimental, biological, and clinical conditions
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
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