19 research outputs found

    Distributed Dendritic Processing Facilitates Object Detection: A Computational Analysis on the Visual System of the Fly

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    Hennig P, Möller R, Egelhaaf M. Distributed Dendritic Processing Facilitates Object Detection: A Computational Analysis on the Visual System of the Fly. PLoS ONE. 2008;3(8): e3092.Background: Detecting objects is an important task when moving through a natural environment. Flies, for example, may land on salient objects or may avoid collisions with them. The neuronal ensemble of Figure Detection cells (FD-cells) in the visual system of the fly is likely to be involved in controlling these behaviours, as these cells are more sensitive to objects than to extended background structures. Until now the computations in the presynaptic neuronal network of FD-cells and, in particular, the functional significance of the experimentally established distributed dendritic processing of excitatory and inhibitory inputs is not understood. Methodology/Principal Findings: We use model simulations to analyse the neuronal computations responsible for the preference of FD-cells for small objects. We employed a new modelling approach which allowed us to account for the spatial spread of electrical signals in the dendrites while avoiding detailed compartmental modelling. The models are based on available physiological and anatomical data. Three models were tested each implementing an inhibitory neural circuit, but differing by the spatial arrangement of the inhibitory interaction. Parameter optimisation with an evolutionary algorithm revealed that only distributed dendritic processing satisfies the constraints arising from electrophysiological experiments. In contrast to a direct dendro-dendritic inhibition of the FD-cell (Direct Distributed Inhibition model), an inhibition of its presynaptic retinotopic elements (Indirect Distributed Inhibition model) requires smaller changes in input resistance in the inhibited neurons during visual stimulation. Conclusions/Significance: Distributed dendritic inhibition of retinotopic elements as implemented in our Indirect Distributed Inhibition model is the most plausible wiring scheme for the neuronal circuit of FD-cells. This microcircuit is computationally similar to lateral inhibition between the retinotopic elements. Hence, distributed inhibition might be an alternative explanation of perceptual phenomena currently explained by lateral inhibition networks

    The Concise Guide to PHARMACOLOGY 2023/24: G protein-coupled receptors.

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    peer reviewedThe Concise Guide to PHARMACOLOGY 2023/24 is the sixth in this series of biennial publications. The Concise Guide provides concise overviews, mostly in tabular format, of the key properties of approximately 1800 drug targets, and about 6000 interactions with about 3900 ligands. There is an emphasis on selective pharmacology (where available), plus links to the open access knowledgebase source of drug targets and their ligands (https://www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. Although the Concise Guide constitutes almost 500 pages, the material presented is substantially reduced compared to information and links presented on the website. It provides a permanent, citable, point-in-time record that will survive database updates. The full contents of this section can be found at http://onlinelibrary.wiley.com/doi/bph.16177. G protein-coupled receptors are one of the six major pharmacological targets into which the Guide is divided, with the others being: ion channels, nuclear hormone receptors, catalytic receptors, enzymes and transporters. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. The landscape format of the Concise Guide is designed to facilitate comparison of related targets from material contemporary to mid-2023, and supersedes data presented in the 2021/22, 2019/20, 2017/18, 2015/16 and 2013/14 Concise Guides and previous Guides to Receptors and Channels. It is produced in close conjunction with the Nomenclature and Standards Committee of the International Union of Basic and Clinical Pharmacology (NC-IUPHAR), therefore, providing official IUPHAR classification and nomenclature for human drug targets, where appropriate

    Youth suicide prevention programs : a resource guide /

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    "September 1992."Includes bibliographical reference (p. 185-190)Mode of access: Internet

    Exploring non-participation in colorectal cancer screening:A systematic review of qualitative studies

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    Introduction: Worldwide, colorectal cancer is a major public health issue. Despite the existence of screening programmes in many countries, global uptake remains low. This meta-ethnography aimed to analyse qualitative literature to explore attitudes towards colorectal cancer screening and reasons for non-participation in eligible people that do not participate when invited. Methods: Systematic searches were conducted in five databases in May 2021. Critical appraisal of included studies was performed using the CASP checklist for qualitative studies. Findings: Thirteen studies were included. Three main themes and eight sub-themes were developed across studies: (1) Differences in motivation, with non-participants expressing a lack of knowledge and varying levels of intention to participate but not feeling screening was personally necessary; (2) Active aversion to screening expressed by fear, discomfort, disgust or not wanting to know; and (3) Contextual barriers of the healthcare system such as practical constraints or poor relationships with healthcare professionals. Conclusion: Findings suggest multiple pathways to non-participation including ambivalence, aversion to the process and consequences of screening or lack of support. Persuasive messages and prompts to action to target ambivalence, reassurance regarding the screening procedures to target negative reactions, and increased support from healthcare professionals may be beneficial in increasing screening uptake.</p
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