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Search Results: 1 - 10 of 191166 matches for " Kyle G. Horn "
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Emergent Central Pattern Generator Behavior in Gap-Junction-Coupled Hodgkin-Huxley Style Neuron Model
Kyle G. Horn,Heraldo Memelli,Irene C. Solomon
Computational Intelligence and Neuroscience , 2012, DOI: 10.1155/2012/173910
Abstract:
Emergent Central Pattern Generator Behavior in Gap-Junction-Coupled Hodgkin-Huxley Style Neuron Model
Kyle G. Horn,Heraldo Memelli,Irene C. Solomon
Computational Intelligence and Neuroscience , 2012, DOI: 10.1155/2012/173910
Abstract: Most models of central pattern generators (CPGs) involve two distinct nuclei mutually inhibiting one another via synapses. Here, we present a single-nucleus model of biologically realistic Hodgkin-Huxley neurons with random gap junction coupling. Despite no explicit division of neurons into two groups, we observe a spontaneous division of neurons into two distinct firing groups. In addition, we also demonstrate this phenomenon in a simplified version of the model, highlighting the importance of afterhyperpolarization currents ( ) to CPGs utilizing gap junction coupling. The properties of these CPGs also appear sensitive to gap junction conductance, probability of gap junction coupling between cells, topology of gap junction coupling, and, to a lesser extent, input current into our simulated nucleus. 1. Introduction Central pattern generators (CPGs) correspond to neural regions that spontaneously generate oscillatory behavior in the absence of patterned input. In both invertebrates and vertebrates, they appear to play a critical role in the formation of repeated oscillatory behaviors, including activities such as walking, swimming, heartbeating, and breathing [1–4]. Because of their roles in cardiac and respiratory function, CPGs may be considered vital for basic survival across much of the animal kingdom. Originally, the oscillatory behaviors seen in locomotion were presumed to be generated through reflexes alone. An ever-growing body of evidence, however, suggests that both locomotor [2, 5] and respiratory oscillatory activities [6, 7] are generated centrally in spinal cord and brainstem regions, respectively, since these behaviors occur in the absence of descending cortical drive and sensory input. Modulation of CPG activity, however, is necessary for adapting locomotor and breathing patterns to ever-changing environmental conditions. Because of this, both the locomotor [8] and the respiratory [9, 10] systems exhibit a great deal of plasticity in the face of changing conditions and, therefore, should be viewed as dynamic rhythm generating devices. Traditionally, reciprocal synaptic inhibition between two neuronal populations (or two groups of neuronal populations, or even two individual neurons [11]) is seen as the standard method of generating CPG behavior in both biological and computational systems. Originally proposed by Brown [12], this style of CPG appears in biological models of lamprey [13] and stick insect locomotion [14]. It also appears in simulated salamander [15] and mammalian locomotion models [16] as well as in leech heart [17] and as a
Application of a “Staggered Walk” Algorithm for Generating Large-Scale Morphological Neuronal Networks
Jack Zito,Heraldo Memelli,Kyle G. Horn,Irene C. Solomon,Larry D. Wittie
Computational Intelligence and Neuroscience , 2012, DOI: 10.1155/2012/876357
Abstract: Large-scale models of neuronal structures are needed to explore emergent properties of mammalian brains. Because these models have trillions of synapses, a major problem in their creation is synapse placement. Here we present a novel method for exploiting consistent fiber orientation in a neural tissue to perform a highly efficient modified plane-sweep algorithm, which identifies all regions of 3D overlaps between dendritic and axonal projection fields. The first step in placing synapses in physiological models is neurite-overlap detection, at large scales a computationally intensive task. We have developed an efficient “Staggered Walk” algorithm that can find all 3D overlaps of neurites where trillions of synapses connect billions of neurons. 1. Introduction Simulating brain structures with large-scale neuronal models lets researchers precisely manipulate features of simulated neural tissues and observe both local and global properties of neural systems. During the last decade, large-scale brain modeling has risen in prominence, with a wide range of publications on brain-scale models[1–3]. Most large-scale modeling research groups focus either on networks that are highly realistic down to the individual axon collaterals and dendrite branches of each neuron [4] or on systems simplified enough to simulate in near real-time on massively parallel hardware [1, 2]. Rather than emphasizing details or simulation speed, our group is more interested in a balanced approach that capitalizes on general structural connectivity and data acquired through multiunit electrode experiments, diffusion tensor imaging, and connectomics studies with stacked slices of brain tissues stained for scanning [4–6]. To develop and test our model-creation code, we have derived parameters for cerebellar models from the detailed connection and density data for the cerebellar cortex in the compendium by Eccles et al. [7]. Large-scale neuronal models range in accuracy from simple, randomly probabilistic networks [8, 9] to realistic neuronal mappings [4]. The level of detail we need for our models is roughly at the tissue level [10], where probabilities of connectivity between distinct volumes of neural tissue and specified neuronal groups can be derived well enough to create alternative models for comparison. The resulting parameters allow for the generation of microcircuitry for particular areas of the brain. The microcircuits can be repeated, with small changes, up to millions of times in some brain regions [10, 11]. A critical and complex part of large-scale neuronal modeling is the
Analyzing the Effects of Gap Junction Blockade on Neural Synchrony via a Motoneuron Network Computational Model
Heraldo Memelli,Kyle G. Horn,Larry D. Wittie,Irene C. Solomon
Computational Intelligence and Neuroscience , 2012, DOI: 10.1155/2012/575129
Abstract:
Analyzing the Effects of Gap Junction Blockade on Neural Synchrony via a Motoneuron Network Computational Model
Heraldo Memelli,Kyle G. Horn,Larry D. Wittie,Irene C. Solomon
Computational Intelligence and Neuroscience , 2012, DOI: 10.1155/2012/575129
Abstract: In specific regions of the central nervous system (CNS), gap junctions have been shown to participate in neuronal synchrony. Amongst the CNS regions identified, some populations of brainstem motoneurons are known to be coupled by gap junctions. The application of various gap junction blockers to these motoneuron populations, however, has led to mixed results regarding their synchronous firing behavior, with some studies reporting a decrease in synchrony while others surprisingly find an increase in synchrony. To address this discrepancy, we employ a neuronal network model of Hodgkin-Huxley-style motoneurons connected by gap junctions. Using this model, we implement a series of simulations and rigorously analyze their outcome, including the calculation of a measure of neuronal synchrony. Our simulations demonstrate that under specific conditions, uncoupling of gap junctions is capable of producing either a decrease or an increase in neuronal synchrony. Subsequently, these simulations provide mechanistic insight into these different outcomes. 1. Introduction Gap junctions are found in a number of areas in the mammalian CNS and are believed to play a significant role in neuronal synchrony [1, 2]. Gap junctions link the intracellular space of two neurons, permitting ions and metabolic molecules to pass between neighboring cells, resulting in a coupling of both electrical and metabolic behavior [3, 4]. These junctions are formed from a hexameric assembly of structural proteins called connexins (Cx), and a number of Cx isoforms, including Cx26, Cx32, Cx36, Cx30.2, Cx45, and Cx50, have been identified in some populations of neurons [5–15]. Of these Cx isoforms, Cx26, Cx32, and Cx36 have been reported to be expressed in neurons and/or motoneurons in respiratory-related CNS regions [9, 11, 12, 14, 16–20]. While many CNS regions have been shown to express Cx proteins or functional gap junction coupling, gap junctions are often present in areas where synchronized firing activity is important. Amongst these CNS regions, brainstem areas associated with central respiratory control (including respiratory-related hypoglossal and phrenic motoneurons), have been shown to express Cx proteins [12, 14, 16–18, 20] or functional coupling [21–23]. Moreover, blockade of gap junctions has been shown to alter not only respiratory activity but also inspiratory-phase neuronal synchrony [24, 25], an observation that is consistent with the idea that the conductance and opening or closing of gap junctions has a direct effect on synchrony of neuronal networks [26]. Intuitively, one
Sources of dietary calcium in patients attending an osteoporosis clinic
Horn G
Nutrition and Dietary Supplements , 2012, DOI: http://dx.doi.org/10.2147/NDS.S31772
Abstract: urces of dietary calcium in patients attending an osteoporosis clinic Short Report (1470) Total Article Views Authors: Horn G Published Date September 2012 Volume 2012:4 Pages 55 - 60 DOI: http://dx.doi.org/10.2147/NDS.S31772 Received: 14 March 2012 Accepted: 12 July 2012 Published: 18 September 2012 Gemma Horn Surgical Department, Perth Royal Infirmary, Perth, Scotland Introduction: Osteoporosis is a common disease that affects both women and men but is more prevalent in postmenopausal women. Reviews suggest that dietary-derived calcium is vital in maintaining adequate calcium balance. Sources of dietary calcium intake among adult patients attending an osteoporosis clinic were reviewed. Method: Two hundred and ninety-one patients attending an osteoporosis clinic were given an eleven-item food questionnaire to complete. The results were compared to the recommended daily allowance of 700 mg. Results: The overall mean intake was 657 mg/day with little difference between age or gender. The best foods for supplying calcium were cheese and milky drinks. Conclusion: This study has confirmed that suboptimal calcium intakes remain common. Dairy sources of calcium remain important. More awareness is needed to convey the importance of dietary calcium and bone health to avoid the development of osteoporosis.
Sources of dietary calcium in patients attending an osteoporosis clinic
Horn G
Nutrition and Dietary Supplements , 2012,
Abstract: Gemma HornSurgical Department, Perth Royal Infirmary, Perth, ScotlandIntroduction: Osteoporosis is a common disease that affects both women and men but is more prevalent in postmenopausal women. Reviews suggest that dietary-derived calcium is vital in maintaining adequate calcium balance. Sources of dietary calcium intake among adult patients attending an osteoporosis clinic were reviewed.Method: Two hundred and ninety-one patients attending an osteoporosis clinic were given an eleven-item food questionnaire to complete. The results were compared to the recommended daily allowance of 700 mg.Results: The overall mean intake was 657 mg/day with little difference between age or gender. The best foods for supplying calcium were cheese and milky drinks.Conclusion: This study has confirmed that suboptimal calcium intakes remain common. Dairy sources of calcium remain important. More awareness is needed to convey the importance of dietary calcium and bone health to avoid the development of osteoporosis.Keywords: osteoporosis, clinic, food questionnaire, calcium, dietary intake, bone health
Bayesian Item Response Analysis of Method-of-Payment Habits in Banking Surveys  [PDF]
Saman Muthukumarana, Kyle Vincent, Jenna G. Tichon
Journal of Mathematical Finance (JMF) , 2019, DOI: 10.4236/jmf.2019.91001
Abstract: Customers have a wide variety of choices in selecting a method of payment in modern society due to advancements in technology. In this paper, we investigate the method of payment habits of banking customers using item response models. We consider three binary item response models used in the literature within the Bayesian framework. These models capture the heterogeneity and complexity of customer perception on methods of payment in different capacities, with different features. For this reason, model assessment methods need to be developed for better inferential purposes. We introduce an assessment criterion based on predictive simulations and illustrate the approach using graphical summary measures. The approach is further highlighted using survey data based on consumer payment choices that was conducted for the Federal Reserve Bank of Boston.
Comparative study on maternal performance of different suckler cow genotypes
G Kelemeri, A Horn
Genetics Selection Evolution , 1980, DOI: 10.1186/1297-9686-12-4-410b
Abstract:
Comparative study on maternal performance of different suckler cow genotypes
Kelemeri G,Horn A
Genetics Selection Evolution , 1980,
Abstract:
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