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Search Results: 1 - 10 of 14848 matches for " Christian Stricker "
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Interaction of short-term depression and firing dynamics in shaping single neuron encoding
Ashutosh Mohan,Mark D. McDonnell,Christian Stricker
Frontiers in Computational Neuroscience , 2013, DOI: 10.3389/fncom.2013.00041
Abstract: We investigated how the two properties short-term synaptic depression of afferent input and postsynaptic firing dynamics combine to determine the operating mode of a neuron. While several computational roles have been ascribed to either, their interaction has not been studied. We considered two types of short-term synaptic dynamics (release-dependent and release-independent depression) and two classes of firing dynamics (regular firing and firing with spike-frequency adaptation). The input–output transformation of the four possible combinations of pre- and post-synaptic dynamics was characterized. Adapting neurons receiving input from release-dependent synapses functioned largely as coincidence detectors. The other three configurations showed properties consistent with integrators, each with distinct features. These results suggest that the operating mode of a neuron is determined by both the pre- and post-synaptic dynamics and that studying them together is necessary to understand emergent properties and their implications for neuronal coding.
Flow Fields: Dense Correspondence Fields for Highly Accurate Large Displacement Optical Flow Estimation
Christian Bailer,Bertram Taetz,Didier Stricker
Computer Science , 2015,
Abstract: Modern large displacement optical flow algorithms usually use an initialization by either sparse descriptor matching techniques or dense approximate nearest neighbor fields. While the latter have the advantage of being dense, they have the major disadvantage of being very outlier prone as they are not designed to find the optical flow, but the visually most similar correspondence. In this paper we present a dense correspondence field approach that is much less outlier prone and thus much better suited for optical flow estimation than approximate nearest neighbor fields. Our approach is conceptually novel as it does not require explicit regularization, smoothing (like median filtering) or a new data term, but solely our novel purely data based search strategy that finds most inliers (even for small objects), while it effectively avoids finding outliers. Moreover, we present novel enhancements for outlier filtering. We show that our approach is better suited for large displacement optical flow estimation than state-of-the-art descriptor matching techniques. We do so by initializing EpicFlow (so far the best method on MPI-Sintel) with our Flow Fields instead of their originally used state-of-the-art descriptor matching technique. We significantly outperform the original EpicFlow on MPI-Sintel, KITTI and Middlebury.
Quantifying impacts of short-term plasticity on neuronal information transfer
Pat Scott,Anna I. Cowan,Christian Stricker
Quantitative Biology , 2012, DOI: 10.1103/PhysRevE.85.041921
Abstract: Short-term changes in efficacy have been postulated to enhance the ability of synapses to transmit information between neurons, and within neuronal networks. Even at the level of connections between single neurons, direct confirmation of this simple conjecture has proven elusive. By combining paired-cell recordings, realistic synaptic modelling and information theory, we provide evidence that short-term plasticity can not only improve, but also reduce information transfer between neurons. We focus on a concrete example in rat neocortex, but our results may generalise to other systems. When information is contained in the timings of individual spikes, we find that facilitation, depression and recovery affect information transmission in proportion to their impacts upon the probability of neurotransmitter release. When information is instead conveyed by mean spike rate only, the influences of short-term plasticity critically depend on the range of spike frequencies that the target network can distinguish (its effective dynamic range). Our results suggest that to efficiently transmit information, the brain must match synaptic type, coding strategy and network connectivity during development and behaviour.
Noradrenergic System Increases Miniature Excitatory Synaptic Currents in the Barrel Cortex
Hashem Haghdoost Yazdi,Mohamad Reza Esmaili,Mohamad Sophiabadi,Christian Stricker
Physiology and Pharmacology , 2007,
Abstract: Introduction: Neurons in layer II and III of the somatosensory cortex in rats show high frequency (33 ± 13 Hz) of miniature excitatory postsynaptic currents (mEPSCs) that their rates and amplitudes are independent of sodium channels. There are some changes in these currents in neurodegenerative and psychological disorders. Regarding to well known roles of the neuromodulatory brain systems in these disorders, study the effects of these systems on the miniature currents provides data to understand more precisely pathogenesis of this disorders. Because cortical neurons receive very dense noradrenergic innervations, we examined effects of noradrenergic system on these currents. Methods: Whole cell patch clamp recordings were made on pyramidal neurons of the barrel cortex from brain slices that continuously superfused with artificial cerebrospinal fluid (ACSF) containing tetrodotoxin, sodium channel blocker and picrotoxin, blocker of the GABA receptors. Results: Application of noradrenalin significantly increased frequency and decreased amplitude of the mEPSCs. Using specific agonists and antagonists of the noradrenergic system, it was determined that the effects are mostly mediated by α1 receptor. Conclusion: Our results showed that noradrenergic system controls sodium channel independent synaptic transmission which can be of importance in regulation and induction of many physiological and pathophysiological conditions.
Induction of Specific Immunotherapy with Hymenoptera Venoms Using Ultrarush Regimen in Children: Safety and Tolerance
Alice K?hli-Wiesner,Lisbeth Stahlberger,Christian Bieli,Tamar Stricker,Roger Lauener
Journal of Allergy , 2012, DOI: 10.1155/2012/790910
Abstract: Background & Objective. Ultrarush induction for specific venom immunotherapy has been shown to be reliable and efficacious in adults. In this study its safety and tolerance in children was evaluated. Methods. Retrospective analysis of 102 ultrarush desensitizations carried out between 1997 and 2005 in 94 children, aged 4 to 15 years. Diagnosis and selection for immunotherapy were according to recommendations of the European Academy of Allergy and Clinical Immunology. Systemic adverse reactions (SARs) were described using the classification of H. L. Mueller. Results. All patients reached the cumulative dose of 111.1?μg hymenoptera venom within 210 minutes. Six patients (6%) had allergic reactions grade I; 2 patients (2%) grade II and 5 patients (5%) grade III. Three patients (3%) showed unclassified reactions. SARs did not occur in the 15 patients aged 4 to 8 years and they were significantly more frequent in girls (29%) compared with boys (12%) ( , multivariant analysis) and in bee venom extract treated patients (20%) compared to those treated with wasp venom extract (8%) (OR 0.33, 95% Cl 0.07–1.25). Conclusion. Initiation of specific immunotherapy by ultrarush regimen is safe and well tolerated in children and should be considered for treating children with allergy to hymenoptera venom. 1. Introduction Hypersensitivity to hymenoptera venom affects approximately 1%–5% of the general population. In Switzerland the prevalence is estimated to be 3.5% in the general population and 0.4%–0.8% in children aged 4 to 16 years. It is one of the three most common causes of immediate type anaphylactic reactions, the other two major causes being drugs and foods [1]. A field sting in a hymenoptera venom allergic patient can cause a spectrum of reactions ranging from severe local swelling to anaphylactic shock with circulatory collapse. Several cases of death are attributed to hymenoptera allergy yearly, mostly in adults. Specific immunotherapy (SIT) is the only known causal treatment for venom-allergic patients [2, 3]. In subjects with a history of generalized reactions to insect sting SIT results in up to 95% rate of protection in wasp venom allergic patients and 80% in bee venom allergic patients [4]. Different protocols have been published for the stepwise increase of the dose of the insect venom during initiation of subcutaneous specific immunotherapy [5–9]: the conventional regime, with injections using increasing doses every one to two weeks over a period of 2 to 4 months, rush immunotherapy extending over approximately 1 week and ultrarush protocols, in which
Irreducibility and efficiency of ESIP to sample marker genotypes in large pedigrees with loops
Soledad A Fernández, Rohan L Fernando, Bernt Guldbrandtsen, Christian Stricker, Matthias Schelling, Alicia L Carriquiry
Genetics Selection Evolution , 2002, DOI: 10.1186/1297-9686-34-5-537
Abstract: (To access the full article, please see PDF)
Arbitrary multi-site two-photon excitation in four dimensions
Vincent Ricardo Daria,Christian Stricker,Richard Bowman,Stephen Redman,Hans-A. Bachor
Physics , 2009, DOI: 10.1063/1.3216581
Abstract: We demonstrate dynamic and arbitrary multisite two-photon excitation in three dimensions using the holographic projection method. Rapid response (fourth dimension) is achieved through high-speed noniterative calculation of the hologram using a video graphics accelerator board. We verify that the projected asymmetric spot configurations have sufficient spatiotemporal photon density for localized two-photon excitation. This system is a significant advance and can be applied to time-resolved photolysis of caged compounds in biological cells and complex neuronal networks, nonlinear microfabrication and volume holographic optical storage.
Identifying signature Zernike modes for efficient light delivery through brain tissue
Sharmila Sane,Julian Choy,Woei Ming Lee,Christian Stricker,Hans Bachor,Vincent Daria
Physics , 2015,
Abstract: Recent progress in neuroscience to image and investigate brain function has been made possible by impressive developments in optogenetic and opto-molecular tools. Such research requires advances in optical techniques for the delivery of light through brain tissue with high spatial resolution. The tissue causes distortions of the wavefront of the incoming light which broadens the focus, thereby reducing the intensity and resolution especially in techniques requiring focal illumination. Adaptive wavefront correction has been demonstrated to compensate for these distortions. However, in many situations iterative derivation of the corrective wavefront introduces time constraints that limit its usefulness when used to probe living cells. Here we demonstrate a direct and fast technique by working with a small set of Zernike modes and demonstrate that corrections derived a priori can lead to significant improvement of the focus. We verify this idea by the electrical response of whole-cell patched neurons following two-photon photolysis of caged neurotransmitters along its dendrites.In particular, we find that the organization of the neuropile in the cortical region of rat brain slicesprovide sufficient a priori information to preselect an effective wavefront correction.
Filament formation associated with spirochetal infection: a comparative approach to Morgellons disease
Middelveen MJ, Stricker RB
Clinical, Cosmetic and Investigational Dermatology , 2011, DOI: http://dx.doi.org/10.2147/CCID.S26183
Abstract: ment formation associated with spirochetal infection: a comparative approach to Morgellons disease Perspectives (16534) Total Article Views Authors: Middelveen MJ, Stricker RB Published Date November 2011 Volume 2011:4 Pages 167 - 177 DOI: http://dx.doi.org/10.2147/CCID.S26183 Marianne J Middelveen, Raphael B Stricker International Lyme and Associated Diseases Society, Bethesda, MD, USA Abstract: Bovine digital dermatitis is an emerging infectious disease that causes lameness, decreased milk production, and weight loss in livestock. Proliferative stages of bovine digital dermatitis demonstrate keratin filament formation in skin above the hooves in affected animals. The multifactorial etiology of digital dermatitis is not well understood, but spirochetes and other coinfecting microorganisms have been implicated in the pathogenesis of this veterinary illness. Morgellons disease is an emerging human dermopathy characterized by the presence of filamentous fibers of undetermined composition, both in lesions and subdermally. While the etiology of Morgellons disease is unknown, there is serological and clinical evidence linking this phenomenon to Lyme borreliosis and coinfecting tick-borne agents. Although the microscopy of Morgellons filaments has been described in the medical literature, the structure and pathogenesis of these fibers is poorly understood. In contrast, most microscopy of digital dermatitis has focused on associated pathogens and histology rather than the morphology of late-stage filamentous fibers. Clinical, laboratory, and microscopic characteristics of these two diseases are compared.
Tracking of industrial objects by using CAD models
Harald Wuest,Didier Stricker
Journal of Virtual Reality and Broadcasting , 2007,
Abstract: In this paper we present a model-based approach for real-time camera pose estimation in industrial scenarios. The line model which is used for tracking is generated by rendering a polygonal model and extracting contours out of the rendered scene. By un-projecting a point on the contour with the depth value stored in the z-buffer, the 3D coordinates of the contour can be calculated. For establishing 2D/3D correspondences the 3D control points on the contour are projected into the image and a perpendicular search for gradient maxima for every point on the contour is performed. Multiple hypotheses of 2D image points corresponding to a 3D control point make the pose estimation robust against ambiguous edges in the image.
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