1,721,010 research outputs found
Cell Type-Specific Targeting Strategies for Optogenetics
No full textAbstract View references (89)
Optogenetic techniques allow versatile, cell type-specific light-based control of cellular activity in diverse set of cells, circuits, and brain structures. Optogenetic actuators are genetically encoded light-sensitive membrane proteins that can be selectively introduced into cellular circuits in the living brain using a variety of genetic approaches. Gene targeting approaches used in optogenetic studies vary greatly in their specificity, their spatial coverage, the level of transgene expression and their potential adverse effects on neuronal cell health. Here, we describe the major gene targeting approaches utilized in optogenetics and provide a simple set of guidelines through which these approaches can be evaluated when designing an in vitro or in vivo optogenetic study. © Springer Science+Business Media LLC 2018
A neural state of resilience? Encoding resilience as set points of cortical microcircuit activity
Get PDFStress resilience describes the capability of an individual to maintain mental health during or after traumatic, stressful or emotionally challenging situations or to return to a mental state similar to that before the crisis onset. The aim of resilience research is to identify mechanisms that enables an individual to maintain mental health, rather than developing mental disorders and has increasingly come into focus. Studies indicate that resilience is an active adaptive process and not just the absence of symptoms observed in individuals who are deficient in these defense mechanisms and therefore susceptible to stressors. Up to date, no universal concept to grasp resilience exists, but several mechanisms that putatively contribute to stress-resilient or -susceptible behavioral phenotypes were identified. In humans, psychological and socio-environmental factors as adaptive coping and social support can contribute to the maintenance of normal psychological function and avoid serious mental illness, but also a wide range of neurobiological markers such as changes in the neuroendocrinological system or genetic factors have been associated with resilience. Yet, to which extend stress resilience is reflected in a differing functional architecture of neuronal network activity remained largely unexplored. There is evidence of hyperactive neuronal network activity within networks of the primary visual cortex (V1) in animal models of multiple sclerosis, Huntington’s or Alzheimer disease, present long before phenotypic changes become measurable at the behavioral level. It is hypothesized that changes in network activity do not serve the purpose to preserve long-term functionality to achieve behavioral functionality but instead aim for short-term stability to maintain the status quo of network function, coining the term of a selfish network. There is mounting evidence that the historic view on brain architecture of distinct brain regions executing well-defined tasks, does not accurately describe brain functionality. Instead, brain regions such as the sensory cortices are considered not only to process incoming sensory stimuli, but also contribute to action execution and decision making, forming a functionally bound brain. The V1 poses a well suitable brain region to probe for network dysregulations as it receives information from other sensory cortices, locomotion and areas related to emotion.
This thesis aims to elucidate the concept of stress-resilience on the level of neuronal networks within V1 in a mouse model of chronic social stress. Mice are subjected to a behavioral paradigm of chronic social defeat (CSD). The behavioral phenotype is assessed by a social interaction-test (SI-test), dividing the population into a resilient and susceptible behavioral phenotype. Furthermore, a subgroup of mice which is not undergoing CSD is used to answer the question if non-stressed animals show neuronal network patterns comparable to resilient or susceptible animals, or whether they represent a third distinct network state. Neuronal network activity is measured in the awake behaving animal on single cell level in V1 layer II/III employing two-photon functional calcium imaging. The assessment of both spontaneous and sensory-evoked neuronal activity is used to obtain a fine-grained picture of the local functional architecture of a network. For improving the sensitivity of the detection of putative network dysregulation, the two-photon functional calcium imaging analysis pipeline has been streamlined and improved, for optimizing the correlation of calcium transient to underlying neuronal action potentials. Lastly, a three-photon functional calcium imaging microscope is implemented and imaging quality is compared with two-photon microscopy modalities.
It was found that the newly developed analysis pipeline outperforms commonly used analysis routines. Employed to functional calcium imaging data in a mouse model of chronic social defeat, neuronal networks in resilient classified animals exhibit lower spontaneous activity and a more accurate representation of visual afferents compared to susceptible litter mates. Non-stressed animals exhibit network activity close to the dynamics of susceptible animals, both in spontaneous network activity as well as in the representation of visual afferents. Lastly, employing three-photon microscopy revealed an increase of the penetration depth at the cost of imaging frequency and size of the resolved field of view.
The findings underline the importance of the development of analysis routines capable of accurately capturing single cell activity to describe neuronal network patterns. In the field of resilience research, the results suggest that architectures of neuronal networks within sensory cortices itself might constitute a resilience mechanism, contributing to the outcome of a resilient or susceptible behavioral phenotype. Finally, the first datasets collected using three-photon microscopy represent a promising opportunity to resolve neuronal networks in deeper regions such as layer V of V1.XXIV, 120 Seiten ; illustrationen, Diagramm
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
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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