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1
Lionetti, Fred. "GPU accelerated cardiac electrophysiology". Diss., [La Jolla] : University of California, San Diego, 2010. http://wwwlib.umi.com/cr/ucsd/fullcit?p1474756.
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Thesis (M.S.)--University of California, San Diego, 2010.Title from first page of PDF file (viewed April 14, 2010). Available via ProQuest Digital Dissertations. Includes bibliographical references (p. 85-89).
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Du, Peng 1985. "Mathematical modelling of gastric electrophysiology". Thesis, University of Auckland, 2011. http://hdl.handle.net/2292/10234.
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This thesis investigates the electrophysiology of the stomach, using a joint experimental and mathematical modelling approach. Normal gastrointestinal (GI) motility is coordinated by multiple cooperating mechanisms, both intrinsic and extrinsic to the GI tract. A fundamental component of the GI motility is an omnipresent electrical activity termed slow waves, which are initiated and propagated by the interstitial cells of Cajal (ICCs) and smooth muscle cells (SMCs). The role of ICC and/or SMC pathophysiology in GI motility disorders is an area of on-going research. This thesis begins with an overview of the functions of the GI tract and slow wave electrophysiology. High-resolution electrode arrays were designed and manufactured using the printed-circuit-board (PCB) technology. The performance of the PCB electrodes were validated against the performance of epoxy-embedded electrodes in porcine subjects, in terms of amplitudes (0.17 vs 0.52 mV), velocity (15.9 vs 13.8 mms-1), and signal-to-noise ratio (9.7 vs 18.7 dB). The PCB electrodes were then used to record gastric slow waves from a number of human subjects. Automatic slow wave activation times identification and velocity calculation techniques were applied to analyse the recorded slow wave data. Analysis of the human data revealed that the gastric slow wave activity originates from a pacemaker region (average amplitude: 0.57 mV ; average velocity: 8.0 mms-1) in the stomach, and continues into the corpus (average amplitude: 0.25 mV ; average velocity: 3.0 mms-1), and then the antrum (average amplitude: 0.52 mV ; average velocity: 5.7 mms-1). The focus of this thesis then shifts to mathematical models of slow wave activity. An existing SMC model was adapted to investigate the effects of gastric electrical stimulation (GES) protocols, in conjunction with experimental recordings in rat antral SMCs. The simulations using the adapted SMC model showed that effective GES protocols could be adapted to include frequency-trains (40 Hz) of short pulse- width (3-6 ms); In a separate study, an existing ICC model was adapted to include a voltage-sensitive inositol 1,4,5-trisphosphate receptor model, which modelled entrainment of slow waves in a network of ICCs; Two coupling mechanisms were also proposed to link the slow waves in the ICC and SMC models. A continuum approach was used to model slow waves in tissue and whole-organ models. The monodomain equation was used to simulate slow wave propagation in a grid of SMCs coupled to a cell automata model, which was used to quantify the entrainment of normal slow wave activity and entrainment of slow waves by a 3.5 cpm GES protocol. The simulation results demonstrated the highest 'zone of entrainment' that could be achieved by the GES protocol was 78% of the modelled tissue area; Next, the bidomain equations were applied to simulate entrainment of slow waves in a wild-type (normal) and a degraded (serotonin receptor knockout) ICC networks obtained from mouse tissue. The ICC network models demonstrated that slow wave propagation was influenced by ICC loss. In addition, compared to the degraded ICC network, the normal ICC network model demonstrated a higher peak current density (1.94 vs 1.45 μAmm-2) as well as [Ca2+]i density (0.67 vs 0.41 mM mm-2), which could help to explain functional impairments that arise when ICC populations are depleted; The human recordings were used to create slow wave activation in a whole organ stomach model. The whole organ model was used as a platform to simulate gastric slow wave propagation, as well as to incorporate physiological characteristics that could not directly measured using the HR technique, such as the variation in the resting membrane potentials of gastric tissues. The final set of modelling studies employed the forward modelling technique to simulate the resultant body surface potential, i.e., electrogastrogram (EGG) of gastric slow waves. A virtual EGG analysis showed that the frequency of EGG matched the underlying slow waves (3 cpm) and the peak potential (-0.63 mV ) in the EGG signal could be correlated to the timing of the full antral activation. This thesis concludes with a discussion on the results and potential future research directions in this field.
3
Jeu, Marcel Theodorus Gerardus de. "Electrophysiology of the suprachiasmatic nucleus". [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2001. http://dare.uva.nl/document/59002.
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Khosrovani, Sara. "Electrophysiology of the olivocerebellar loop". [S.l.] : Rotterdam : [The Author] ; Erasmus University [Host], 2008. http://hdl.handle.net/1765/12220.
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Malchano, Zachary John. "Image guidance in cardiac electrophysiology". Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/35515.
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Thesis (M. Eng.)--Harvard-MIT Division of Health Sciences and Technology, 2006.MIT Institute Archives copy: Pages 101-130 bound in reverse order.
Includes bibliographical references (p. 123-130).
Cardiac arrhythmias are characterized by a disruption or abnormal conduction of electrical signals within the heart. Treatment of arrhythmias has dramatically evolved over the past half-century, and today, minimally-invasive catheter-based therapy is the preferred method of eliminating arrhythmias. Using an electroanatomical (EA) mapping system, which precisely tracks the position of catheters inside the patient's body, it is possible to construct three-dimensional maps of the ventricular and atrial chambers of the heart. Each point of these maps is annotated based on bioelectrical signals recorded from the electrodes located at the tip of the catheter. These maps are then used to guide catheter ablation within the heart. However, the electroanatomical mapping procedure results in relatively sparse sampling of the heart and a significant amount of time and skill are require to generate these maps. In this thesis, we present our software system for the integration of pre-operative, patient-specific magnetic resonance (MR) or computed tomography (CT) imaging data with real-time electroanatomical mapping (EAM) information.
(cont.) Following registration between the EAM and imaging data, the system allows for real-time catheter navigation within patient-specific anatomy. We then evaluate candidate registration strategies to rapidly and accurately align the pre-operative imaging data with the intra-operative mapping data using simulated electroanatomical mapping data using the great cardiac vessels including the aorta, superior vena cava, and coronary sinus. Based on these in vitro results, we focus on a registration strategy which is constrained by the ascending and descending aorta. In vivo prospective evaluation of the resulting image integration was then performed (n>200) in both experimental and clinical electrophysiology procedure. To compensate for residual error following registration or patient movement during a procedure, we present and evaluate warping strategies for deforming the pre-operative imaging data into agreement with the intra-operative mapping information.
by Zachary John Malchano.
M.Eng.
6
Leudar, Augustine Jan Seth Maranatha Bannatyne. "Integrating plant electrophysiology and sonic art". Thesis, Queen's University Belfast, 2017. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.727419.
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This thesis accompanies a portfolio of site specific sound art installations that were delivered in the UK, Europe and South America between 2012 and 2016. The principle focus of the research is to combine plant electrophysiology and sonic art with a particular emphasis on spatial audio. By using networks of electrodes, audio spatialisation and various artistic techniques, electrical activity in the biosphere was made tangible through sound in real-time. Installations based on this research were presented at public events, immersing listeners in the complexity of these processes. Bespoke software was created to meet creative and technical objectives. Sound installations were created that were designed to stand as works of art in their own right regardless of whether or not the audience knew there was a scientific component to the piece; at the same time new approaches to monitoring electrical activity in plants were developed. A description of how these two elements are combined and how scientific needs influence artistic work and vice versa is given. The principle object of this research is not to gather qualitative or quantitative data, but to convert signals into sound in real-time and create art installations that engender a space where independent elements of both disciplines can merge as well as develop independently from each other. Technical and artistic gaps in the field are identified through the literature review and addressed in the installations. The software created forms a bridge between the creative and the technical side of the research and is described by means of videos. This commentary is accompanied by a USB stick that has relevant software and audio documentation. It also includes an offline website which contains important information such as videos, and is referred to throughout the text and forms an essential component of the thesis.
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Roy, Thomas. "Time-Stepping Methods in Cardiac Electrophysiology". Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32626.
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Modelling in cardiac electrophysiology results in a complex system of partial differential equations (PDE) describing the propagation of the
electrical wave in the heart muscle coupled with a highly nonlinear system of ordinary differential equations (ODE) describing the ionic
activity in the cardiac cells. This system forms the widely accepted bidomain model or its slightly simpler version, the monodomain model.
To a large extent, the stiffness of the whole model depends on the choice of the ionic model, which varies in terms of complexity and
realism. These simulations require accurate and, depending on the ionic model used, possibly very stable numerical methods. At this time,
solving these models numerically requires CPU time of around one day per heartbeat. Therefore, it is necessary to use the most efficient
method for these simulations.
This research focuses on the comparison and analysis of several time-stepping methods: explicit or semi-implicit, operator splitting, deferred correction and Rush-Larsen methods. The goal is to find the optimal method for the ionic model used. For our analysis, we used the monodomain model but our results apply to the bidomain model as well. We compare the methods for three ionic models of varying complexity and stiffness: the Mitchell-Schaeffer models with only 2 variables, the more realistic Beeler-Reuter model with 8 variables, and the stiff
and very complex ten Tuscher-Noble-Noble-Panfilov (TNNP) models with 17 variables. For each method, we derived absolute stability criteria of the spatially discretized monodomain model and verified that the theoretical critical time steps obtained closely match the ones in numerical experiments. Convergence tests were also conducted to verify that the numerical methods achieve an optimal order of convergence on the model variables and derived quantities (such as speed of the wave, depolarization time), and this in spite of the local non-differentiability of some of the ionic models. We looked at the efficiency of the different methods by comparing computational times for similar accuracy. Conclusions are drawn on the methods to be used to solve the monodomain model based on the model stiffness and complexity, measured respectively by the most negative eigenvalue of the model's Jacobian and the number of variables, and based on strict stability and accuracy criteria.
8
Wang, Linwei. "Noninvasive imaging of 3D cardiac electrophysiology /". View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?ECED%202007%20WANGL.
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Blaetz, Taylor S. "The Electrophysiology of Written Informal Language". TopSCHOLAR®, 2015. http://digitalcommons.wku.edu/theses/1513.
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Language is an essential component of human behavior. It is ubiquitous, but more importantly, it is malleable and it is constantly changing. Part of the dynamic nature of informal communication is the introduction and adoption of new linguistic elements. Online communication provides a window into this informal public discourse; therefore, it may be useful for testing hypotheses about the processes underlying the acquisition and use of new words. The comprehension of informal language may lead to an understanding of how these new informal words are integrated into our mental lexicon. The current study was an electroencephalographic (EEG) investigation of the brain processes that underlie informal language. We recorded event-related potentials while participants engaged in a lexical decision task. For this experiment, participants made judgments about Twitter targets primed with semantically related or unrelated words. Classic psycholinguistic studies have shown very specific event-related potentials (ERPs) for semantic processing. Most notably, the N400 event-related potential component is an index of lexical expectancy and semantic relatedness. In contrast to the literature, we did not find classic N400 priming effects. However, our results revealed marked differences between informal and traditional targets. Our results suggest that informal language is more difficult to process than traditional language.
10
Morris, Andrew Paul. "The electrophysiology of mammalian salivary glands". Thesis, University of Liverpool, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279746.
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Rakkah, N. I. A. "Electrophysiology of isolated mammalian spinal cord". Thesis, University of Southampton, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233185.
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Chen, Tsai Yuan. "Network Electrophysiology Sensor-On-A- Chip". Digital WPI, 2011. https://digitalcommons.wpi.edu/etd-dissertations/389.
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"
Electroencephalogram (EEG), Electrocardiogram (ECG), and Electromyogram (EMG) bio-potential signals are commonly recorded in clinical practice. Typically, patients are connected to a bulky and mains-powered instrument, which reduces their mobility and creates discomfort. This limits the acquisition time, prevents the continuous monitoring of patients, and can affect the diagnosis of illness. Therefore, there is a great demand for low-power, small-size, and ambulatory bio-potential signal acquisition systems.
Recent work on instrumentation amplifier design for bio-potential signals can be broadly classified as using one or both of two popular techniques: In the first, an AC-coupled signal path with a MOS-Bipolar pseudo resistor is used to obtain a low-frequency cutoff that passes the signal of interest while rejecting large dc offsets. In the second, a chopper stabilization technique is designed to reduce 1/f noise at low frequencies. However, both of these existing techniques lack control of low-frequency cutoff.
This thesis presents the design of a mixed- signal integrated circuit (IC) prototype to provide complete, programmable analog signal conditioning and analog-to-digital conversion of an electrophysiologic signal. A front-end amplifier is designed with low input referred noise of 1 uVrms, and common mode rejection ratio 102 dB. A novel second order sigma-delta analog- to-digital converter (ADC) with a feedback integrator from the sigma-delta output is presented to program the low-frequency cutoff, and to enable wide input common mode range of ¡Ãƒâ€œ0.3 V. The overall system is implemented in Jazz Semiconductor 0.18 um CMOS technology with power consumption 5.8 mW from ¡Ãƒâ€œ0.9V power supplies. "
13
Zhang, Ke. "Cardiac electrophysiology and cardiotoxicity of halothane /". The Ohio State University, 1989. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487676261012213.
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Golas, Lillian B. "Mechanosensory neurons in culture : morphology and electrophysiology". Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56638.
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Crustacean mechanosensory neurons, isolated by enzymatic digestion from abdominal muscle receptor organs of Homarus americanus and Procambarus clarkii, maintain characteristic morphological and electrophysiological phenotypes in culture. New outgrowth occurs at both the axonal and dendritic poles. The patterns of outgrowth are distinct and in keeping with the sensory function. The cut axonal end gives rise to few elongated processes which rarely branch. In contrast, the new growth at the dendritic pole consists of multiple, short ($<$10 um) processes which resemble normal sensory termini. Cultured tonic and phasic sensory neurons respond to depolarizing current injections with characteristic firing patterns. Single channel patch clamp studies have identified at least four different ion channels. In Homarus, three channel types are voltage but not stretch sensitive. One channel type identified in Procambarus, displays both voltage and stretch sensitivity. These cultured mechanosensory neurons have the potential to be useful models for the study of the mechanisms of mechanotransduction.
15
Talbot, Hugo. "Interactive patient-specific simulation of cardiac electrophysiology". Thesis, Lille 1, 2014. http://www.theses.fr/2014LIL10056/document.
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Dans cette thèse, le premier challenge consiste à simuler l'électrophysiologie cardiaque en temps-réel. Une implémentation GPU innovante permet cela et celle-ci est appliquée à un patient souffrant d'un bloc de branche gauche. Les activités électrique et mécanique caractéristiques de cette pathologie sont ainsi reproduite in silico. Une seconde étape de ce travail se concentre sur la personnalisation du modèle d'électrophysiologie cardiaque afin de reproduire de manière rapide et précise l'activité électrique d'un patient. Enfin, cette thèse présente le développement d’un framework d’entrainement à l’ablation radiofréquence d’arythmies cardiaques. Basé sur les simulations patient-spécifiques d’électrophysiologie, ce simulateur vise à entrainer in silico des électrophysiologistes non-expérimentés et ainsi accélérer leur apprentissage. Ce système d’entrainement inclut une phase de navigation endovasculaire et la simulation d’une arythmie cardiaque qu’il faut virtuellement traiter. Une évaluation clinique a été menée auprès de cardiologistes et les resultats attestent des bonnes performances et du réalisme du simulateur. Ce travail est donc un premier pas vers des outils d’entrainement basés sur la simulationThe objective of this thesis is to construct a training framework, allowing junior electrophysiologists to practice radio-frequency ablation for the treatment of ventricular arrhythmia on virtual patients. The first challenge consists in simulating the cardiac electrophysiology in real-time. A powerful GPU implementation is proposed to reach real-time performances. A realistic left bandle branch block can be simulated, thus inducing the associated late contraction of the left ventricle. For clinical application of electrophysiological mathematics, this GPU simulation needs to be personalized. This crucial step aims at adapting all model parameters in order to fit patient data. Our personalization is achieved in about 20 minutes and relies on an Unscented Kalman filter applied iteratively on the clinical data. Lastly, the construction of the first training framework dedicated to cardiac ablation is presented. An innovative multithreading approach couples the simulation of cardiac electrophysiology and catheter navigation. A clinical evaluation performed by electrophysiologists highlights the good performances and the realism of the training framework. This framework is a first step towards realistic and efficient virtual training systems in cardiology
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Wetter, Spencer Ryan. "Olfactory psychophysics and electrophysiology in Huntington's Disease /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2003. http://wwwlib.umi.com/cr/ucsd/fullcit?p3083456.
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Leroy, Félix. "Atteinte différentielle de deux populations de motoneurones spinaux chez le souriceau SOD1 G93A (modèle de la maladie de Charcot)". Thesis, Paris 5, 2013. http://www.theses.fr/2013PA05T063/document.
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La deuxième semaine qui suit la naissance est critique pour le développement du système locomoteur de la souris. C’est pendant cette semaine que les souriceaux acquièrent leur posture et commencent à marcher. Cette transformation implique une réorganisation en profondeur des éléments composant les unités motrices. Cependant, nous ne savons encore que peu de choses sur la différenciation des propriétés intrinsèques des motoneurones innervant les fibres musculaires. Contrairement à l’adulte, où la décharge démarre au début de la stimulation, les motoneurones de souriceaux déchargent de façon hétérogène. En effet, une stimulation au seuil induit chez certains motoneurones une décharge commençant au début du créneau alors que la décharge est retardée dans d’autres motoneurones. Par des enregistrements de motoneurones sur des tranches de moelle épinière à P6-P10, j’ai dans un premier temps caractérisé les courants sous‐tendant la décharge retardée et j’ai constaté que deux conductances potassiques (l’une ressemblant au courant de type A et l’autre très lente) étaient activées autour du seuil de décharge. Lorsqu’elles s’activent, ces conductances sont capables d’hyperpolariser le potentiel de membrane et d’empêcher le motoneurone de décharger. Puis, en s’inactivant, la membrane se dépolarise et le neurone commence à décharger avec un retard pouvant aller jusqu’à plusieurs secondes après le début du créneau. En outre, les deux populations de motoneurones présentent des propriétés électro-physiologiques et morphologiques différentes. Les motoneurones à décharge retardée possèdent un arbre dendritique plus ramifié que ceux à décharge immédiate. En conséquence, les motoneurones à décharge retardée possèdent une conductance d’entrée et un seuil de recrutement plus faible. De plus le temps de relaxation de l’hyperpolarisation suivant chaque potentiel d’action (AHP) est plus long dans les motoneurones à décharge immédiate. Enfin, une partie des motoneurones à décharge retardée exprime la protéine chondrolectine récemment décrite comme un marqueur moléculaire des motoneurones de type rapide. L’ensemble de nos résultats nous permet de faire l’hypothèse que les motoneurones à décharge retardée sont des motoneurones innervant les unités motrices de type rapide alors que ceux à décharge immédiate innervent les unités motrices de type lent. Dans un second temps, j’ai étudié l’effet de la mutation SOD1 G93A, un modèle murin de la sclérose latérale amyotrophique, sur les motoneurones spinaux à P6‐P10. Sachant que cette maladie affecte les motoneurones de façon différente à l’âge adulte, j’ai cherché à savoir si, chez les souriceaux SOD1 G93A, les motoneurones à décharge retardée et immédiate étaient affectés de la même façon. Mes résultats montrent que seuls les motoneurones à décharge immédiate sont hyperexcitables. Pour ces motoneurones, le seuil de décharge est plus hyperpolarisé et leurs dendrites sont plus courtes de 35%. Ces résultats amènent à reconsidérer le lien supposé entre hyperexcitabilité et dégénérescence des motoneuronesIn the second postnatal week, the locomotor behavior of mice changes from crawling to walking. This is made possible by profound changes in motor units. Yet, how the discharge properties of spinal motoneurons evolve during post-‐natal maturation and whether they have an effect on the motor unit maturation remains an open question. In neonates, the spinal motoneurons display two modes of discharge. For threshold pulses, 33% of the motoneurons have a discharge that start at the current onset and adapts during the pulse (“immediate firing motoneurons”). The remaining 66% motoneurons fire with a large delay and the discharge then accelerates throughout the pulse (“delayed firing motoneurons”). Though the delayed firing pattern is quite common in spinal motoneurons of neonates, the ionic mechanisms that elicit this mode of discharge have received little attention. Using the patch-clamp technique to record P6‐P10 mouse motoneurons in a spinal cord slice preparation, I characterized the ionic currents that underlie the delayed firing pattern. This is caused by a combination of an A-like potassium current that acts on a short time scale and a slow‐inactivating potassium current that delays the discharge on a much longer time scale. I then investigated how these two potassium currents contribute to the recruitment threshold and how they shape the F-I function of delayed motoneurons in neonatal mice. The slow inactivating potassium current induces memory effects that have a strong impact on motoneuron excitability and on its discharge. Building on these results, I tried to correlate the discharge pattern to known physiological sub‐types. The delayed firing motoneurons have a larger input conductance, a higher rheobase, a narrower action potential, a shorter AHP and a more complex dendritic arbor than the immediate firing motoneurons. Additionally, only a sub-‐population of the delayed firing motoneurons expressed the chondrolectin protein, a fast motoneuron marker. Based on this body of corroborating evidence, the immediate firing motoneurons would be slow type motoneurons whereas the delayed firing motoneurons would be fast type motoneurons. Finally, numerous electrical and geometrical abnormalities have been observed in spinal motoneurons of SOD1 G934 mice (model of the amyotrophic lateral sclerosis) during the second post-natal week but the results were somehow contradictory. In relation to the known differential sensitivity to the disease exhibited by slow and fast motoneurons, I investigated whether the immediate and delayed firing motoneurons are equally affected by the SOD1 mutation. This is not the case. I found that the SOD1 mutation induced a decrease in the rheobase and a hyperpolarization of the voltage threshold only in the immediate firing motoneurons, thereby making them more excitable than in WT mice. Furthermore, the dendrites of the immediate firing motoneurons are substantially shorter (about 35%) in the mutant than in the WT. In sharp contrast, the excitability of the delayed firing motoneurons is unchanged and the dendritic tree is nearly unaffected (the dendrites only undergo a 10% elongation). These results allow for reconsidering the link between hyperexcitability and degenerescence of the motoneurons
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Fiancette, Jean-Francois. "Electrophysiologie multi-site et optogénétique appliquées à l’étude de corrélats neurobiologiques de l’addiction à la cocaïne chez le rat se comportant". Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0901/document.
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L’addiction se caractérise par une recherche et une consommation pathologiques de la drogue, maintenues malgré leurs conséquences néfastes. C’est une pathologie chronique car, le plus souvent, les tentatives de sevrage se soldent par une rechute. L’addiction à la cocaïne se développe chez 15 à 20 % des usagers, après un usage plus ou moins prolongé. Les solutions thérapeutiques font gravement défaut et c’est un enjeu que de comprendre les mécanismes neurobiologiques qui sous-tendent cette addiction. Les études cliniques et précliniques proposent que l’addiction résulte d’un déséquilibre entre les circuits cortico-subcorticaux qui gèrent la valeur motivationnelle de la drogue et ceux qui sont impliqués dans le contrôle cognitif inhibiteur. Des changements séquentiels dans des circuits interconnectés qui incluent notamment le noyau basolatéral de l’amygdale, le noyau accumbens et le cortex préfrontal seraient au cœur de processus motivationnels pathologiques et d’une difficulté à inhiber le craving et la consommation. L’étude de l’addiction, à l’échelle des circuits neuronaux, fait face à plusieurs défis. Techniquement limitée chez l’homme, elle peut bénéficier des modèles animaux, mais seulement s’ils capturent des dimensions de la pathologie. Au cours des dix dernières années, de tels modèles ont été mis en œuvre, mais exclusivement chez le rat. Or, les outils pour l’exploration fonctionnelle fine des circuits neuronaux ont été majoritairement développés chez la souris. Un autre défi consiste à pouvoir questionner la fonctionnalité des circuits, en temps réel, sur l’individu se comportant. Mes travaux de thèse ont eu pour objectif : 1. L’étude de marqueurs de connectivité fonctionnelle chez des rats Addict et des rats Non-addict à la cocaïne. Notre modèle d’addiction à la cocaïne permet d’identifier 15 à 20 % de rats qui, après une période prolongée d’autoadministration intraveineuse de cocaïne, et bien qu’ils aient consommé la même quantité de cocaïne que les autres, montrent une très forte motivation pour la substance, une difficulté à limiter la recherche de drogue, et maintiennent la prise de cocaïne malgré ses conséquences néfastes. L’électrophysiologie in vivo, multi-site, au moyen d’enregistrements unitaires ou de potentiels de champs locaux est un outil de choix pour l’exploration de la connectivité fonctionnelle chez le rongeur. Un défi technique a été de l’adapter pour la coupler à notre modèle d’addiction à la cocaïne chez le rat. Nous avons montré des différences significatives de connectivité fonctionnelle entre rats Addict et Non-addict, suggérant un défaut de fonctionnalité du cortex préfrontal médian (PFM) chez les Addict. 2. L’étude du rôle du cortex prélimbique (PL) dans le contrôle du comportement d’autoadministration de cocaïne chez le rat. Des données récentes de la littérature remettent en cause le dogme selon lequel le PL exerce exclusivement un rôle facilitateur sur les propriétés motivationnelles de la cocaïne. Nous avons cherché à clarifier le rôle du PL dans le comportement d’autoadministration de cocaïne avant que ne se développe une addiction : comprendre son rôle dans l’usage précoce de cocaïne pour, à terme, étudier l’évolution de son implication selon que l’individu développe ou non une addiction. Nous avons montré que l’inactivation du PL peut s’accompagner, chez le même individu, d’une diminution ou d’une exacerbation du comportement de recherche de cocaïne selon les contingences expérimentales. Les neurones du PL émettent des projections vers plusieurs structures. Pour étudier leur rôle dans les effets comportementaux observés, nous avons travaillé à la mise au point d’outils optogénétiques pour la manipulation de l’activité de voies neuronales spécifiques, chez le rat, pour lequel ils sont encore très peu développés. Mes travaux de thèse contribuent tant sur le plan théorique que technique à la compréhension des mécanismes psychobiologiques de l’addiction à la cocaïneDrug addiction is characterized by pathological drug seeking and taking, maintained despite their negative consequences. This is a chronic pathology, withdrawal attempts being unsuccessful in most cases. Cocaine addiction develops in about 15 to 20 % of habitual users. For cocaine, therapeutic options are lacking, which could be explained by the relatively poor understanding of the neurobiological mechanisms underlying cocaine addiction to date. Clinical and preclinical studies propose that addiction results from an imbalance between the cortical-subcortical circuits that process motivational value of drug-related stimuli versus those involved in cognitive inhibitory control. Hierarchical sequential changes in distinct, but interconnected circuits, including the basolateral amygdala, the nucleus accumbens and the prefrontal cortex could be at the core of pathological incentive processes and difficulty to control craving and drug taking. Studying addiction at the neuronal circuit level faces many challenges. Technically limited in humans, it can benefit from animal models, but only if they properly capture dimensions of the pathology. Over the last ten years, such models have been developed, but exclusively in rats. However, tools for a refined functional exploration of neuronal circuits have been established mostly in mice, and until recently they have begun to be explored in rats. In addition, another main challenge is the ability to investigate functional connectivity in real time in behaving animals. My thesis work had two objectives: 1. Studying markers of functional connectivity in rats showing a cocaine addiction-like behavior (Addict) or not (Non-addict). Our model of cocaine addiction allows identifying 15-20% of rats that show a high motivation for cocaine, a difficulty to limit drug seeking and that maintain drug taking despite negative consequences. These extreme behaviors occur after prolonged cocaine self-administration and despite that these rats have used a comparable amount of cocaine as compared to the others. In vivo, multi-site electrophysiology recordings, applied to single units or local field potentials, is a tool of choice for studying functional connectivity in rodents. A technical challenge has been to adapt and couple it to our model of cocaine addiction in the rat. We have evidenced significant differences in connectivity between Addict and Non-addict rats, which suggest a default of functionality of the medial prefrontal cortex in the Addict rats. 2. Studying the role of the prelimbic cortex (PL) in cocaine self-administration behavior in the rat. The canonical role of the PL in exclusively promoting drug seeking was recently questioned, with studies involving it also in inhibition of drug seeking. Our first goal was to clarify this role of the PL in early cocaine self-administration, i.e. before addiction-like behavior develops: understanding its early role to eventually compare it to its late role and whether an addiction-like behavior develops or not. We have shown that optogenetic PL inactivation can decrease or increase cocaine seeking in the same individual, according to experimental contingencies. PL neurons project to several remote structures. To study the role of these different neuronal pathways, we have worked in establishing optogenetic tools for the manipulation of specific neuronal pathways, in the rat, for which they are still poorly developed. My thesis work contribute, both theoretically and technically, to the understanding of the psychobiology of cocaine addiction
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Li, Pan. "Multiscale Modelling of Mammalian Uterine and Cardiac Electrophysiology". Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491646.
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Broman, Daniel. "Lateralization of human olfaction : cognitive functions and electrophysiology". Doctoral thesis, Umeå : Department of Psychology, Umeå University, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-861.
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Sachse, Frank B. "Computational cardiology : modeling of anatomy, electrophysiology, and mechanics /". Berlin [u.a.] : Springer, 2004. http://www.loc.gov/catdir/enhancements/fy0818/2004104242-d.html.
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Saphier, D. J. "Electrophysiology and endocrine function of rat tuberoinfundibular neurones". Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373694.
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Cooper, Patricia J. "Stretch effects on cardiac electrophysiology : chronotropy and arrhythmogenesis". Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.442383.
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Brownson, Kathleen. "INVESTIGATION OF CARDIAC ELECTROPHYSIOLOGY IN HUMAN VENTRICULAR TISSUE". UKnowledge, 2014. http://uknowledge.uky.edu/cbme_etds/16.
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Individuals with cardiomyopathy are at higher risk to die from sudden cardiac arrest than those with non-failing (NF) hearts. This study examined the differences in electrical properties of failing and NF human hearts in terms of cardiac memory through explicit control of diastolic intervals in a sinusoidal fashion, restitution of action potential duration (APD) through standard and dynamic pacing protocols, maximum rate of depolarization and APD alternans. Recordings of transmembrane potentials were made in tissues extracted from patients with heart failure and one donor NF heart. Computational simulations were performed using the O’Hara Rudy model for generating surrogates of control data. Significant differences were seen between left ventricular (LV) tissue and NF LV tissue in tilt, and measures of memory in terms of area and thickness during the sinusoidal 400ms protocol. Minimum delay was also significantly higher in the failing LV during the sinusoidal 150ms protocol. Failing tissues showed a higher restitution slope and prolonged AP which is consistent with previous studies and is hypothesized to contribute to the increased susceptibility to unstable alternans. This study further explored how disease alters the electrical functioning of the heart and why these patients are at a higher risk of ventricular arrhythmia.
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Grice, Sarah-Jane. "The electrophysiology of face perceptions in Williams Syndrome". Thesis, University College London (University of London), 2002. http://discovery.ucl.ac.uk/1317671/.
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Williams Syndrome is a rare genetic disorder in which the processing of faces and visual 'perception' has been argued to be intact despite other 'deficits' of visuospatial processing. In contrast, the theoretical approach taken in this thesis argues that the brains of those with developmental disorders cannot be legitimately viewed in terms of sparing and impairment, but must be considered as having atypical properties emergent as a result of atypical development. The event-related potential technique is used to provide evidence of abnormalities of perception of visual stimuli, including faces, even within the first 250ms of processing. A new approach to the brain imaging of people with developmental disorders is discussed. The thesis concludes by proposing an 'abnormal binding' hypothesis which aims to explain the nature and neural basis of the visuo-cognitive processing abnormalities in Williams Syndrome.
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Kirby, Ian K. "Ticker-2 : a Qualitative Model of cardiac electrophysiology". Thesis, University of Aberdeen, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293110.
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Ticker-2 is a Qualitative Model of cardiac electrophysiology. One of the motivations was a desire to test and improve Qualitative Modelling techniques by their application to a real-world problem. The approach used is component-based, but, unlike much other work in Qualitative Modelling, discrete valued parameters are used. The application of temporal constraints play an important part, and the Relative Endpoint Duration formalism has been developed to constrain the generation of behaviours by the application of knowledge about the domain. This formalism is unusual in Qualitative Modelling in that an explicit 'unknown' value is used, instead of allowing uncertain values to lead to nondeterministic branching. Both simulation and envisionment have been used to generate behaviours from Ticker-2. Problems exist with both, but envisionment being more appropriate to the domain of cardiac electrophysiology, a number of ways of overcoming difficulties with envisionment are developed. An approach to comparing the behaviours of Ticker-2 with KARDIO behaviours is also suggested.
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Constantinescu, Mihaela. "Computer-assisted electroanatomical guidance for cardiac electrophysiology procedures". Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/59668.
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Cardiac arrhythmias are serious life-threatening episodes affecting both the aging population and younger patients with pre-existing heart conditions. One of the most effective therapeutic procedures is the minimally-invasive catheter-driven endovascular electrophysiology study, whereby electrical potentials and activation patterns in the affected cardiac chambers are measured and subsequent ablation of arrhythmogenic tissue is performed. Despite emerging technologies such as electroanatomical mapping and remote intraoperative navigation systems for improved catheter manipulation and stability, successful ablation of arrhythmias is still highly-dependent on the operator’s skills and experience. This thesis proposes a framework towards standardisation in the electroanatomical mapping and ablation planning by merging knowledge transfer from previous cases and patient-specific data. In particular, contributions towards four different procedural aspects were made: optimal electroanatomical mapping, arrhythmia path computation, catheter tip stability analysis, and ablation simulation and optimisation. In order to improve the intraoperative electroanatomical map, anatomical areas of high mapping interest were proposed, as learned from previous electrophysiology studies. Subsequently, the arrhythmic wave propagation on the endocardial surface and potential ablation points were computed. The ablation planning is further enhanced, firstly by the analysis of the catheter tip stability and the probability of slippage at sparse locations on the endocardium and, secondly, by the simulation of the ablation result from the computation of convolutional matrices which model mathematically the ablation process. The methods proposed by this thesis were validated on data from patients with complex congenital heart disease, who present unusual cardiac anatomy and consequently atypical arrhythmias. The proposed methods also build a generic framework for computer guidance of electrophysiology, with results showing complementary information that can be easily integrated into the clinical workflow.
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Ocholi, Ojonimi A. "An intracardiac navigation interface for electrophysiology modeling tools". Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/37083.
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Thesis (M. Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.Includes bibliographical references (p. 79-81).
This thesis describes an interface that has been developed to assist in medical procedures. Several commercial systems are currently available each with their own strength and weaknesses and the goal of this interface is to leverage each of them. It is based upon a number of toolkits such as the Visualization Toolkit (VTK) and the GUI development tool QT. To facilitate the rapid deployment of highly modular applications, an Application Programming Interface (API) was created and modeled after the Model-View-Controller paradigm. The interface was then built using this API into an executable application and it provides various features such as accurate catheter navigation and the registration of data from different sources. In addition, the interface was used to investigate the accuracy of one commercial system (LocaLisa) with regards to another (CARTO).
by Ojonimi A. Ocholi.
M.Eng.and S.B.
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Amos, D. P. "Effects of cannabinoids and novelty on hippocampal electrophysiology". Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1335611/.
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Exposure to novel environments alters hippocampal cell and theta local field potential activity to support the formation of new or updated spatial representations. It induces remapping of place cell fields, a reduction in CA1 theta frequency and an increase in the spatial scale of entorhinal grid cell fields. A recent model proposes that a reduction in the slope of the theta frequency-running speed relationship (TFRSR) can account for these effects (Burgess, 2008, Hippocampus). In contrast, the model proposes that the Y-axis intercept of the TFRSR is unaffected by novelty but instead correlates with anxiety/arousal. Thus, the theta frequency reduction elicited by a wide range of anxiolytic drugs (Gray & McNaughton, 2000) is suggested to result from a decrease in the intercept. Cannabinoids are anxiolytic at low doses, reduce theta frequency and disrupt the theta-timescale dynamics of place cell firing. In contrast, environmental novelty elicits a coordinated shift in CA1 place cell firing to a later theta-phase. This thesis examines the electrophysiological effects of environmental familiarity or novelty in combination with a low, intraperitoneal dose of the cannabinoid agonist O-2545, or its vehicle, saline. It was found that exposure to novel environments reduced the slope of the TFRSR whereas the cannabinoid reduced the intercept, in agreement with the model. These effects were not due to decreased body temperature or changes in behaviour. Combining novelty and drug reduced both slope and intercept. Furthermore, the extent of novelty-induced place cell remapping correlated with the reduction in slope. The mean theta-phase of place cell firing shifted later in novelty, but this was disrupted by the cannabinoid. In contrast, the mean theta-phase of the interneuron population was stable across conditions, but novelty increased the dispersion of interneuron theta-phase preferences. These results help to elucidate the mechanisms underlying novelty processing and cannabinoid action in the hippocampus.
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Walmsley, John. "Incorporating inter-sample variability into cardiac electrophysiology simulations". Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:6c653c3c-64e8-4337-bb97-728b99361573.
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Sudden cardiac death kills 5-10 people per 10,000 population in Europe and the US each year. Individual propensity to arrhythmia and sudden cardiac death is typically assessed through clinical biomarkers. Variability in these biomarkers is a major challenge for risk stratification. Variability is observed at a wide range of spatio-temporal scales within the heart, from temporal fluctuations in ion channel behaviour, to inter-cell and inter-regional differences in ion channel expression, to structural differences between hearts. The extent to which variability manifests between spatial and temporal scales remains unclear but has a potentially crucial role in determining susceptibility to arrhythmia. In this dissertation we present a multi-scale study of the causes and consequences of variability in electrophysiology. At a sub-cellular level we demonstrate that, taking into account inter-individual variability in ion channel conductance, mRNA expression levels in failing human hearts predict the electrophysiological remodelling observed experimentally. On a tissue scale, we advocate the use of phenomenological models where information on subcellular processes is unavailable. We introduce a modification to a phenomenological model to capture beat-to-beat variability in action potential repolarisation recorded from four individual guinea pig myocytes. We demonstrate that, whilst temporal variability is dramatically reduced by inter-cell coupling, differences in their mean action potential duration may become apparent at a tissue level. The ventricular myocardium has a heterogeneous structure not captured by the simplified representation of conduction used above. In our final case study, we challenge a model of conduction by directly comparing simulations to optical mapping recordings of ventricular activation from failing and non-failing human hearts. We observe that good fits to experimental data are obtained only when endocardially bound structures are not in view, suggesting a role in conduction for these structures that are often ignored in cardiac simulations. Finally, we present future directions for the work presented. We make the case for reporting of inter-sample variability in experimental results and conclude that whilst variability may not always manifest across scales, its impact should be considered in both theoretical and experimental studies.
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McManigle, John E. "Three-dimensional geometric image analysis for interventional electrophysiology". Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:2f36fa8e-9c64-4807-97c0-25e63398da7e.
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Improving imaging hardware, computational power, and algorithmic design are driving advances in interventional medical imaging. We lay the groundwork here for more effective use of machine learning and image registration in clinical electrophysiology. To achieve identification of atrial fibrosis using image data, we registered the electroanatomic map (EAM) data of atrial fibrillation (AF) patients undergoing pulmonary vein isolation (PVI) with MR (n = 16) or CT (n = 18) images. The relationship between image features and bipolar voltage was evaluated using single-parameter regression and random forest models. Random forest performed significantly better than regression, identifying fibrosis with area under the receiver operating characteristic curve (AUC) 0.746 (MR) and 0.977 (CT). This is the first evaluation of voltage prediction using image data. Next, we compared the character of native atrial fibrosis with ablation scar in MR images. Fourteen AF patients undergoing repeat PVI were recruited. EAM data from their first PVI was registered to the MR images acquired before the first PVI (‘pre-operative’) and before the second PVI ('post-operative' with respect to the first PVI). Non-ablation map points had similar characteristics in the two images, while ablation points exhibited higher intensity and more heterogeneity in post-operative images. Ablation scar is more strongly enhancing and more heterogeneous than native fibrosis. Finally, we addressed myocardial measurement in 3-D echocardiograms. The circular Hough transform was modified with a feature asymmetry filter, epicardial edges, and a search constraint. Manual and Hough measurements were compared in 5641 slices from 3-D images. The enhanced Hough algorithm was more accurate than the unmodified version (Dice coefficient 0.77 vs. 0.58). This method promises utility in segmentation-assisted cross-modality registration. By improving the information that can be extracted from medical images and the ease with which that information can be accessed, this progress will contribute to the advancing integration of imaging in electrophysiology.
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McNiven, Alistair Iain. "Electrophysiology of potassium channels in the hamster egg". Thesis, University of Edinburgh, 1989. http://hdl.handle.net/1842/29885.
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Vaughan, Parker Andrew. "Electrophysiology of Optic Nerves in Methylglyoxal Treated Mice". Wright State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=wright1590769538838536.
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Robinson, Rebecca Louise. "Experimental study of electrophysiology using the fEITER system". Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/experimental-study-of-electrophysiology-using-the-feiter-system(399260d4-6c11-4227-9633-4d76f933e5af).html.
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Within neurophysiology, there is need for improvements to functional brain imaging devices. Neural processing within the brain occurs on milli-second through to second timescales. Currently there are no systems with the sufficient temporal resolution and depth sensitivity. Electrical impedance tomography (EIT) is a technique that offers milli-second imaging, depth sensitivity, portability and low cost. It is already applied routinely in other medical applications such as lung function monitoring and breast imaging. The research presented in this thesis has contributed to the design and development of a 32-electrode EIT system, known as fEITER (functional Electrical Impedance Tomography of Evoked Responses). fEITER has been designed to be a brain imaging device that has a temporal resolution of 100 fps with an overall SNR of greater than 70 dB operating at 10 kHz. In order to carry out human tests using fEITER, the system required applications to the local and national ethics (NRES) as well as safety standards regulation (MHRA). These processes were successfully completed, receiving a 'notice of no objection' for a clinical trial using fEITER at The University of Manchester and Manchester Royal Infirmary. A series of tank tests were analysed as a method of understanding the system performance. The data obtained from human tests showed unique results. The reference data showed a repeating 'saw tooth' that is time-locked to the heart beat of the volunteer, which is a novel observation in medical EIT. Furthermore, the auditory stimuli data showed topographical differences across the scalp with respect to the startle and controlled auditory stimuli. These observations are based on single-event evoked responses, which is unique within the field of evoked potential studies. From the observations reported in this thesis it is plausible that fEITER is measuring voltages changes that are due to the neural processing.
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Matthews, Brian. "Micromachined planar patch-clamp system for electrophysiology research". Diss., Restricted to subscribing institutions, 2006. http://proquest.umi.com/pqdweb?did=1188879521&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Arzounian, Dorothée. "Sensory variability and brain state : models, psychophysics, electrophysiology". Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCB055/document.
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La même entrée sensorielle ne provoque pas toujours la même réaction. Dans les expériences en laboratoire, un stimulus donné peut engendrer une réponse différente à chaque nouvel essai, en particulier à proximité du seuil sensoriel. Ce phénomène est généralement attribué à une source de bruit non spécifique qui affecte la représentation sensorielle du stimulus ou le processus décisionnel. Dans cette thèse, nous examinons l'hypothèse selon laquelle cette variabilité des réponses peut être attribuée en partie à des fluctuations mesurables et spontanées de l'état cérébral. Dans ce but, nous développons et évaluons deux ensembles d'outils. L’un est un ensemble de modèles et de méthodes psychophysiques permettant de suivre les variations de la performance perceptive avec une bonne résolution temporelle et avec précision, sur différentes échelles de temps. Ces méthodes s’appuient sur des procédures adaptatives initialement développées pour mesurer efficacement les seuils de perception statiques et sont étendues ici dans le but de suivre des seuils qui varient au cours du temps. Le deuxième ensemble d'outils que nous développons comprend des méthodes d'analyse de données pour extraire de signaux d’électroencéphalographie (EEG) une quantité prédictive de la performance comportementale à diverses échelles de temps. Nous avons appliqué ces outils à des enregistrements conjoints d’EEG et de données comportementales collectées pendant que des auditeurs normo-entendants réalisaient une tâche de discrimination de fréquence sur des stimuli auditifs proche du seuil de discrimination. Contrairement à ce qui a été rapporté dans la littérature concernant des stimuli visuels, nous n'avons pas trouvé de preuve d’un quelconque effet des oscillations EEG spontanées de basse fréquence sur la performance auditive. En revanche, nous avons trouvé qu'une part importante de la variabilité des jugements peut s’expliquer par des effets de l'historique récent des stimuli et des réponses sur la décision prise à un moment donnéThe same sensory input does not always trigger the same reaction. In laboratory experiments, a given stimulus may elicit a different response on each trial, particularly near the sensory threshold. This is usually attributed to an unspecific source of noise that affects the sensory representation of the stimulus or the decision process. In this thesis we explore the hypothesis that response variability can in part be attributed to measurable, spontaneous fluctuations of ongoing brain state. For this purpose, we develop and test two sets of tools. One is a set of models and psychophysical methods to follow variations of perceptual performance with good temporal resolution and accuracy on different time scales. These methods rely on the adaptive procedures that were developed for the efficient measurements of static sensory thresholds and are extended here for the purpose of tracking time-varying thresholds. The second set of tools we develop encompass data analysis methods to extract from electroencephalography (EEG) signals a quantity that is predictive of behavioral performance on various time scales. We applied these tools to joint recordings of EEG and behavioral data acquired while normal listeners performed a frequency-discrimination task on near-threshold auditory stimuli. Unlike what was reported in the literature for visual stimuli, we did not find evidence for any effects of ongoing low-frequency EEG oscillations on auditory performance. However, we found that a substantial part of judgment variability can be accounted for by effects of recent stimulus-response history on an ongoing decision
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Tschabrunn, Michael Cory. "Electrophysiologic characterization of the arrhythmogenic substrate in re-entrant atrial and ventricular arrhythmias : insights from the clinical and experimental electrophysiology laboratories". Thesis, City, University of London, 2016. http://openaccess.city.ac.uk/17437/.
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This thesis encompasses an overview and critical analysis of 11 publications of clinical and translational cardiac electrophysiology research that has been executed over the last seven years. The focus of this dissertation and the selected papers is on the use of electroanatomic mapping technology to define the arrhythmogenic substrate in patients with structural heart disease and ventricular arrhythmias. Such advancements in elucidating the mechanisms and pathophysiology underlying scar-related ventricular tachycardia have yielded improved clinical outcomes for patients with drug-refractory ventricular arrhythmias. Chapter 1 describes the epidemiologic background and introduces the concept of intracardiac mapping and the technological evolution that has provided the basis for this current body of work. Chapter 2 and Chapter 3 provide a detailed description of how electroanatomic mapping studies have provided critical insight into disease pathogenesis in patients with dilated nonischemic cardiomyopathy arrhythmogenic right ventricular cardiomyopathy (ARVC). The clinical impact and relevance of these studies are discussed based on conventional electroanatomic mapping technologies to define abnormal physiological substrates. Chapter 3 also addresses important considerations regarding percutaneous epicardial mapping and ablation that have been derived from extensive clinical experience. Chapter 4 and Chapter 5 describe the evolution of mapping technologies and the use of high-resolution mapping system technologies. These chapters discuss the potential clinical advantages of these technologies during substrate and activation mapping, particularly in post-infarct ventricular scar and VT. Finally, Chapter 6 concludes this thesis with final thoughts on the broader context of the lessons that have been learned from the studies that are presented in this thesis and implications for future work.
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Duchateau, Josselin. "Traitement et analyse du signal pour les arythmies ventriculaires". Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0465/document.
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Les techniques de traitement du signal numérique prennent une place grandissante en rythmologie clinique. Ces outils offrent de nouvelles perspectives d'amélioration de la détection d'anomalies rythmiques subtiles et d'interprétation des arythmies complexes. Notre travail se focalise sur l'apport des techniques de traitement du signal pour les arythmies ventriculaires. Il s'intéresse à trois champs complémentaires: les signaux unidimensionnels (ECG et EGM), la cartographie non-invasive, et la cartographie invasive. Concernant les signaux unidimensionnels, nous proposons tout d'abord une méthodologie d'amélioration du rapport signal sur bruit des enregistrements ECG par des méthodes de moyennage et de gating respiratoire. Cette méthodologie offre des perspectives intéressantes pour [a détection de signaux anormaux de faible amplitude et pour la mesure non-invasive de l'intervalle HV. Nous détaillons ensuite les liens entre signaux endocardiques et ECG en fibrillation ventriculaire (FV), en montrant notamment que les fréquences dominantes sont fortement corrélées et qu'une fragmentation endocardique se traduit sur l'ECG de surface par une chute de l'amplitude. Enfin, nous démontrons par une analyse fréquentielle de 63épisodes de FV le lien entre les caractéristiques de ces épisodes et les caractéristiques cliniques des patients qui en sont victimes. Notamment, la fréquence dominante est très corrélée à la cardiopathie sous jacente. Le mode et le site d'induc tion ont également un impact important sur l'arythmie, aussi bien sur les fréquences que le degré de fragmentation et la phase de l'ECG de surface. Concernant la cartographie non-invasive, nous présentons une comparaison de différentes méthodes de résolution en potentiel du problème inverse. Cette comparaison démontre que la méthodologie ECGi fait partie des meilleures approches évaluées. Nous proposons ensuite une étude de validation des cartes d'activation ventriculaires par ECGi dans un contexte clinique sur 55 patients. Cette étude retrouve une corrélation médiocre entre les cartes non-invasives et les cartes de référence. Les résultats sont hétérogènes, avec une bonne corrélation sur les rythmes avec QRS larges. Nous proposons ensuite quelques pistes d'amélioration de ces cartes d'activation, par une analyse nouvelle de la solution fondamentale ECGi qui s'intéresse au gradient et au laplacien du potentiel et par un post-traitement des potentiels reconstruits, en combinant une évaluation des délais entre points voisin avec une mesure locale de temps d'activation. Ces deux techniques permettent une amélioration significative de la qualité des cartes reconstruites. Concernant la cartographie invasive, nous nous intéressons aux domaines et aux techniques d'inter polation de mesures ponctuelles. Nous montrons l'importance de ces techniques sur le rendu final d'une carte d'activation. Nous utilisons ensuite une de ces méthodologies pour produire des cartes améliorées chez les patients porteurs d'un syndrome de Brugada. Nous montrons qu'il existe chez ces patients des arguments cliniques en faveur d'un bloc partiel de conduction endo-épicardique prédominant au niveau de l'infundibulum et de la partie latérobasale du ventricule droit. Enfin, nous montrons à l'aide d'un modèle in silico les conséquences arythmogènes d'une telle dis sociation, qui se traduit par une inductibilité accrue lorsque le nombre de connexions fonctionnelles résiduelles diminue. Au TOTAL, notre travail utilise les techniques de traitement du signal pour différentes applications autour des arythmies ventriculaires. Nous proposons plusieurs innovations méthodologiques permettant d'extraire et de traiter de manière nouvelle le signal électrique cardiaque. Les techniques de cartographie non-invasives doivent encore être améliorées pour tenir toutes leurs promesses. L'électrocardiographie et la cartographie de contact pourront voir leur champ d'utilisation étendu par ces innovationsSignal processing tools are increasingly present in the electrophysiologist' s daily practice. These tools have the potential to enhance the detection of small electrical anomalies, and to enable the analysis of complex arrhythmia. Our work focuses on ventricular arrhythmia, and more specifically on how signal processing tech niques can help usbetter understand these diseases. lt is made up of three parts,focusing on different topics: uni-dimensional signal analysis (ECG and endocardial electrograms), non-invasive mapping, and invasive contact mapping. Concerning uni-dimensional signal analysis, we first propose a method to enhance the signal to noise ratio of ECG recordings. We use a combination of signal averaging and respiration gating to achieve this goal, and offer interesting perspectives for the detection of abnormal low amplitude potentials and non-invasive measurement of the HV interval. We then analyze the relationship between endocardial and ECG signais during ventricular fibrilla tion (VF) episodes. We demonstrate that endocardial and ECG dominant frequencies are similar,and that higher endocardial fragmentation results in a drop of the waveform amplitude on the surface ECG. Finally, we demonstrate through frequency domain analysis of 63 VF episodes a clear correlation between VF characteristics and clinical factors. Dominant frequency is particularly useful to dis criminate between different underlying causal substrates. We also demonstrate that VF characteris tics depend on the induction mode and induction site, in terms of dominant frequency, amount of fragmentation and ECG phase. Concerning non-invasive mapping, we compare different potential-based inverse problem resolution techniques. ECGi appears as one of the most reliable techniques. A clinical validation study of non-invasive ventricular activation mapping using ECGi isthen carried out. Fifty-five patients were included for whom non-invasive maps are compared to contact maps. We show a very poor overall correlation between non-invasive and invasive maps. Results are het erogeneous, with good correlation in patients with wide QRS activation patterns. Wethen propose different techniques to improve non-invasive activation mapping. A first study uses the surface laplacian and the gradient of the inverse-computed potential as inputs to activation map ping. A second study combines estimated delays between neighboring points and local activation time estimates to create a more globally coherent solution. Both studies demonstrate a significant improvement of activation maps. Concerning contact mapping, we first give an overview of interpolation domains and techniques that can be used to provide dense activation maps from sparse measures. We illustrate the influence of these techniques on the clinician's ability to make a correct diagnosis. We then use one of these interpolation techniques to create epicardial activation maps in Brugada patients. We show that these patients harbor epicardial electrical activity compatible with partial endo-epicardial conduction block. This phenomenon predominates in the right ventricular lateral wall and outflow tract. Finally,using an in silico model, we demonstrate the arrhythmogenic potential of such a dissociation. lnducibility peaks as the number of residual functional connections between endo and epicardium falls. ÜVERALL, our work uses signal processing techniques for different applications conceming ven tricular arrhythmia. We propose different methodological innovations that allow us to record and process cardiac electrical activity with increasing precision. Further progress is still required before non-invasive mapping can live up to its promises. The proposed methodological innovations can extend the use of electrocardiography and invasive mapping
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Knecht, Sébastien. "Contribution à la compréhension des mécanismes électrophysiologiques de la fibrillation auriculaire et application pour le traitement invasif percutané". Doctoral thesis, Universite Libre de Bruxelles, 2010. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/241306.
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Ross, Patricia. "Electrophysiology of working memory, task modality and load effects". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ51224.pdf.
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De, Roode Michael R. "The effects of Taurine depletion on rat heart electrophysiology /". Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59626.
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Taurine is an amino acid found in high concentration (20-30 mM) in mammalian heart. Treatment of rats with the transport antagonist guanidinoethyl sulfonate (GES) depletes cardiac taurine ($>$70%). Electrocardiograms were recorded weekly in restrained unanaesthetized rats. GES treatment caused a selective prolongation of the QT interval which was correlated with the degree of myocardial taurine depletion (r$ sp2$ = 0.92, p $<$ 0.001). Ventricular muscle action potential durations (APD$ sb{95}$) from taurine-depleted hearts were significantly prolonged compared to control (88 +/- 8 ms vs. 66 +/- 9 ms; p $<$ 0.001). Taurine supplements given to depleted rats reversed the taurine depletion and the QT prolongation; no effect was seen in controls. No action potential differences between control and "reversed" rats were seen. Superfusion of GES or taurine at concentrations of 0.2-10 mM had no effect on action potential characteristics of control or taurine-depleted hearts. When hamsters were GES-treated no cardiac biochemical or QT changes were seen.
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Richards, Christopher David. "Electrophysiology and electrochemistry of substantia nigra neurones in vitro". Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259895.
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Smith, P. A. "Electrophysiology of #beta#-cells form the islets of Langerhans". Thesis, University of East Anglia, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380117.
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Roche, Michael Geoffrey. "Electrophysiology of cortical spreading depression in the rat neocortex". Thesis, Boston University, 2012. https://hdl.handle.net/2144/12604.
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Thesis (M.A.)--Boston UniversityCortical spreading depression (CoSD) is a reaction of the cerebral cortex to injury and neuropathology. It is comprised of self propagating waves of neuronal hyperexcitability, followed by a pronounced and lasting depression of the electrical activity. This depression travels outward from the initiation source across the surface of the brain at a rate of 2-5 mm/min and is accompanied by a shift in the direct current potential. To better understand the mechanism behind CoSD, intra-cortical electrophysiological recording techniques were used to test the hypothesis that CoSD produces a layer-specific effect on the rat cortex. A linear multi-electrode was used to examine coherent neural activity at all levels of the primary visual cortex before, during and after CoSD. In addition, evoked neural activity was assessed by the use of paired pulse stimulation to the contralateral primary visual cortex. The effect of CoSD on the frequency content of the neural signals was also investigated. Finally, current source density analysis of the evoked signal was examined to determine whether CoSD produced alterations in the location or magnitude of where the evoked currents entered (current sinks) and left (current sources) the cortical laminae. CoSD was reliably induced, but the effects were short, only lasting for the first five minutes post initiation. Immediately following the initiation of CoSD, the first peak of the evoked potential was reduced, indicating that the excitability of the cortex was reduced by CoSD. After a period of time passed, the first peak returned to baseline while the second peak increased. The paired pulse index (ratio of the amplitude of the first evoked signal to the amplitude of the second evoked signal) was highly reduced and showed a lasting effect, indicating a reduction in the evoked inhibitory tone. This reduction in inhibitory tone was accompanied by alterations in the evoked gamma and beta bands, and a reduction in the alpha, which likely contributed in part to the reduction of the first peak. The spontaneous measured frequency bands showed a selective decrease in alpha, beta and theta, whereas gamma and delta were unaffected. All these were not specific to individual cortical lamina, but occurred at every laminae. Finally, current source density analysis showed that the CoSD did not induce any immediate or lasting changes in the pattern or magnitude of the current sinks and sources. These findings show that CoSD induces highly specific changes in the cortex, but does so in a uniform manner throughout the cortical width. The paired pulse data in conjunction with the results of the frequency analysis also suggests that CoSD causes a decrease in the efficacy of the cortical inhibitory networks. Frequency analysis further suggests that CoSD is possibly associated with a functional disconnection between the cortex and the thalamus. These data are the first to show the effects of CoSD using intracortical recordings and further the understanding of CoSD.
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Bernstein, Jacob (Jacob Gold). "Development of extracellular electrophysiology methods for scalable neural recording". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/107581.
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Thesis: Ph. D., Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references.
In order to map the dynamics of neural circuits in mammalian brains, there is a need for tools that can record activity over large volumes of tissue and correctly attribute the recorded signals to the individual neurons that generated them. High-resolution neural activity maps will be critical for the discovery of new principles of neural coding and neural computation, and to test computational models of neural circuits. Extracellular electrophysiology is a neural recording method that has been developed to record from large populations of neurons, but well-known problems with signal attribution pose an existential threat to the viability of further system scaling, as analyses of network function become more sensitive to errors in attribution. A key insight is that blind-source separation algorithms such as Independent Component Analysis may ameliorate problems with signal attribution. These algorithms require recording signals at much finer spatial resolutions than existing probes have accomplished, which places demands on recording system bandwidth. We present several advances to technologies in neural recording systems, and a complete neural recording system designed to investigate the challenges of scaling electrophysiology to whole brain recording. We have developed close-packed microelectrode arrays with the highest density of recording sites yet achieved, for which we built our own data acquisition hardware, developed with a computational architecture specifically designed to scale to over several orders of magnitude. We also present results from validation experiments using colocalized patch clamp recording to obtain ground-truth activity data. This dataset provides immediate insight into the nature of electrophysiological signals and the interpretation of data collected from any electrophysiology recording system. This data is also essential in order to optimize probe development and data analysis algorithms which will one day enable whole-brain activity mapping.
by Jacob G. Bernstein.
Ph. D.
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Canham, Amy Elizabeth. "Toward accessible evaluation of the electrophysiology of human vision". Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/91431.
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Thesis: S.M., Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 75-77).
As photoreceptors in our retinas capture discrete photons, that energy is converted into an electrochemical signal which shoots back through the optic nerve and into our visual cortex. We can sample that signal as it's transmitted, by delivering specific stimuli and recording the aggregate response of the photoreceptors, but systems which accomplish this in current practice are out of reach for most ophthalmic clinics and completely unavailable to consumers. With a reimagined signal capture system and an optimized system design, I demonstrate a robust method for capturing the electrical signals emitted from the retina. With the improved accessibility and decreased cost of this technology, there are immediate opportunities for improved ophthalmic care on a broad scale. But beyond the clinical implications, accessible electroretinography presents an unprecedented opportunity for individuals to characterize their specific experience of color, contrast, and movement, making way for a whole new paradigm of tailored display technologies.
by Amy Elizabeth Canham.
S.M.
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Panayiotou, Maria. "Motion gating for X-ray guided interventional electrophysiology procedures". Thesis, King's College London (University of London), 2015. http://kclpure.kcl.ac.uk/portal/en/theses/motion-gating-for-xray-guided-interventional-electrophysiology-procedures(70729d75-40ba-4886-b333-f5b1c5bf3556).html.
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Atrial fibrillation (AF) is a common supraventricular arrhythmia, characterized by irregular and uncoordinated contraction of the atrium. Although AF itself is not lethal, it accounts for secondary diseases and morbidity and mortality. The minimally-invasive radiofrequency ablation (RFA) procedure is a commonly performed treatment option for AF, guided by Xray fluoroscopy. While it provides high temporal and spatial resolution, X-ray fluoroscopy has poor soft-tissue contrast. In order to enhance image guidance, volumetric roadmaps overlaid on live X-ray fluoroscopy may be used. However, these roadmaps are often static and do not reflect cardiorespiratorymotion. Real-time roadmap update is important to compensate for this motion and maintain the accuracy of the guidance information, thereby allowing accurate determination of catheter-based ablation treatment sites. Motion gating is crucial for achieving this accuracy. Four novel and clinically applicable robust-to-noise motion gating techniques are developed and presented in this thesis. The first proposed technique, Tracked-principal component analysis (PCA), is based on the formation of a novel statistical model of the motion of a coronary sinus (CS) catheter using PCA of tracked electrode locations from monoplane X-ray fluoroscopy images. Motion gating was later further extended to be applicable to more types of minimally invasive procedures, such as Cardiac resynchronisation therapy, where the CS catheter is not present in the X-ray images. This is achieved by the development of two robust to varying image-content techniques, the hierarchical manifold learning based and the Masked-PCA techniques. To avoid the limitation of the requirement to build a separate model for each X-ray view, an X-ray system View-angle independent technique was developed based on learning CS catheter motion using PCA and then applying the derived motion model to unseen images taken at arbitrary projections. Applications of the motion gating techniques spanning from basic research to clinical tasks are demonstrated. These include catheter reconstruction in 3D from catheter tracking in gated sequential biplane X-ray images that can effectively achieve 2D/3D registration of 3D cardiac data (CT or MRI) to X-ray fluoroscopy; motion gating of 3D rotational X-ray angiography sequences where the angulation of the scanner is changed between frames; and motion compensation on unseen images taken at any arbitrary projection, by integrating cardiorespiratory motion into MRI-derived roadmaps fused with live X-ray fluoroscopy. This thesis is devoted to the development of robust-to-noise motion gating techniques and their use for improved procedure guidance while at the same time minimising patient and staff exposure to radiation, by allowing the use of lower-dose fluoroscopy. Results indicate that, within the constraints of acceptable accuracy, the achievable dose reduction factor is 1/25 for the HML-based and Masked-PCA techniques, indicating a dose reduction of more than 25 times, between 1/10 and 1/25 for the Tracked-PCA technique and around 1/10 for the View-angle independent technique.
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Ali, Rheeda. "Calibration of a personalised model of left atrial electrophysiology". Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/48053.
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Patient-specific computer models of the human atria have the potential to aid clinical intervention in the treatment of cardiac arrhythmias if suitably validated. An anatomically accurate, patient-specific map of the electrical conductivity of the left atrial tissue is obtained using data from delayed-enhancement magnetic resonance imaging (MRI), and validated against clinical electroanatomic mapping measurements. The patient-specific intensity maps from two accepted image segmentation and registration techniques are evaluated and compared, and the approach is shown to be highly sensitive to the technique used. The segmentation technique and direction of the maximum intensity projection are both critical in interpreting regions of fibrosis from the patient specific intensity maps. The clinical data suggests a linear relationship between the intensity and the local conduction velocity, which is incorporated into the atrial model through calibration of the conductivity tensor. Simulations of the resulting atrial models produce activation patterns that strongly correlate with clinical recordings. A novel semi-automated algorithm is used for landmark selection for image registration for spatially comparing the electroanatomical and MRI based images. The thesis concludes with a discussion of using the resulting computational model to interrogate the underlying structural and functional substrates of patients with atrial fibrillation.
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Khalbuss, Walid E. "Electrophysiology, Cell Calcium, and Mechanisms of Hepatocyte Volume Regulation". Digital Commons @ East Tennessee State University, 1990. https://dc.etsu.edu/etd/2709.
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The electrophysiologic technique (Reuss, L., Proc. Natl. Acad. Sci. USA 82:6014, 1985) was modified to measure changes in steady-state hepatocyte volume during osmotic stress. Hepatocytes in mouse liver slices were loaded with tetramethylammonium ion (TMA$\sp{+}$) during transient exposure of cells to nystatin. Intracellular TMA$\sp{+}$ activity (a$\sp{\rm i}\sb{\rm TMA}$) was measured with TMA$\sp{+}$-sensitive, double-barreled microelectrodes. Loading hepatocytes with TMA$\sp{+}$ did not change their membrane potential (V$\sb{\rm m}$), and under steady-state conditions a$\sp{\rm i}\sb{\rm TMA}$ remained constant over 4 min in single impalements. Hyperosmotic solutions (50, 100, & 150 mM sucrose added to media) and hyposmotic solutions (sucrose in media reduced by 50 & 100 mM) increased and decreased a$\sp{\rm i}\sb{\rm TMA}$, respectively, which suggested transmembrane water movements. The regression coefficient of the ratio of control a$\sp{\rm i}\sb{\rm TMA}$/experimental a$\sp{\rm i}\sb{\rm TMA}$ versus the relative osmolality of media (experimental mOsm/control mOsm) was -0.34 $\pm$ 0.03, p $<$ 0.001, which is less than expected for a perfect osmometer. Corresponding measurements of V$\sb{\rm m}$ showed that its magnitude increased with hyposmolality and decreased with hyperosmolality. When Ba$\sp{2+}$ (2 mM) was present during hyposmotic stress of 0.66 $\times$ 286 mOsm (control), cell water volume increased by a factor of 1.44 $\pm$ 0.02 compared with that of hyposmotic stress alone, which increased cell water volume by a factor of only 1.12 $\pm$ 0.02, p $<$ 0.001. Ba$\sp{2+}$ also decreased the hyperpolarization of V$\sb{\rm m}$ due to hyposmotic stress from a factor of 1.62 $\pm$ 0.04 to 1.24 $\pm$ 0.09, p $<$ 0.01. When verapamil (50 $\mu$M) was present during hyposmotic stress of 0.69 $\times$ 292 mOsm (control), cell water volume increased by a factor of 1.42 $\pm$ 0.02 compared with that of hyposmotic stress alone, which increased cell water volume by a factor of only 1.19 $\pm$ 0.02, p $<$ 0.001. Verapamil also decreased the hyperpolarization of V$\sb{\rm m}$ due to hyposmotic stress from a factor of 1.34 $\pm$ 0.07 to 1.08 $\pm$ 0.08, p $<$ 0.05. Similar results were obtained when exposing hepatocytes to Ca$\sp{2+}$-free medium plus EGTA (5 mM). It was concluded that hepatocytes partially regulate their steady-state volume during hypo- and hyperosmotic stress. However, volume regulation during hyposmotic stress diminished along with hyperpolarization of V$\sb{\rm m}$ in the presence of the K$\sp{+}$-channel blocker, Ba$\sp{2+}$, the Ca$\sp{2+}$-channel blocker, verapamil and the Ca$\sp{2+}$-chelator, EGTA. This indicated that cell calcium and membrane potassium conductance (g$\sb{\rm K}$) were involved in hepatocyte volume regulation mechanism and that variation in V$\sb{\rm m}$ provides an intercurrent, electromotive force for hepatocyte volume regulation.
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Tixier, Eliott. "Variability modeling and numerical biomarkers design in cardiac electrophysiology". Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066325/document.
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Cette thèse de doctorat est consacrée à l'étude de la variabilité observée dans les mesures d'électrophysiologie (i.e. l'activité électrique des tissus biologiques) cardiaque et à la conception de biomarqueurs numériques extraits de ces mesures. Les applications potentielles sont nombreuses, pouvant aller d'une meilleure compréhension des modèles électrophysiologiques existants à l'évaluations des effets nocifs de médicaments en passant par le diagnostic de pathologies cardiaques. Les modèles d'électrophysiologie cardiaque présentés dans ce travail sont, soit des équations différentielles ordinaires (EDOs), soit des équations aux dérivées partielles (EDPs), selon qu'ils concernent l'échelle cellulaire ou l'échelle du tissu. Dans les deux cas, ces modèles sont hautement non linéaires et nécessitent d'intenses ressources computationnelles. Nous adoptons l'approche suivante : de prime abord, nous développons des outils numériques afin de répondre à des problèmes généraux, au-delà de l'électrophysiologie. Puis, nous appliquons ces outils à des mesures synthétiques d'électrophysiologie dans différents scénarios réalistes et, lorsque cela est possible, à des mesures expérimentales. Dans la première partie de cette thèse, nous présentons une méthode générale pour estimer la densité de probabilité de paramètres incertains de modèles basés sur des EDOs ou des EDPs. La méthode est non intrusive et repose sur des évaluations "hors-ligne" du modèle direct, ce qui la rend en pratique computationellement moins dispendieuse que d'autres approches plus sophistiquées. La méthode est illustrée avec des mesures synthétiques et expérimentales d'électrophysiologie. Dans la seconde partie de cette thèse, nous présentons une méthode de sélectionde biomarqueurs à partir des sorties de modèles en vue d'effectuer des tâches de classification ou de résoudre des problèmes d'estimation de paramètres. La méthode repose sur la résolution d'un problème d'optimisation creux. La méthode est illustrée avec des modèles simples et ensuite appliquée à des mesures synthétiques, incluant des enregistrements d'électrocardiogramme, et à des données expérimentales obtenues à partir de mesures de matrices de microélectrodesThis PhD thesis is dedicated to the study of the variability observed in cardiac electrophysiology (i.e. the electrical activity of biological tissues) measurements and to the design of numerical biomarkers extracted from these measurements. The potential applications are numerous, ranging from a better understanding of existing electrophysiology models to the assessment of adverse effects of drugs or the diagnosis of cardiac pathologies. The cardiac electrophysiology models considered in the present work are either ODEs or PDEs depending on whether we focus on the cell scale or the tissue scale. In both cases, these models are highly non-linear and computationally intensive. We proceed as follows: first we develop numerical tools that address general issues and that are applicable beyond the scope of cardiac electrophysiology. Then, we apply those tools to synthetic electrophysiology measurements in various realistic scenarios and, when available, to real experimental data. In the first part of this thesis, we present a general method for estimating the probability density function (PDF) of uncertain parameters of models based on ordinary differential equations (ODEs) or partial differential equations (PDEs). The method is non-instrusive and relies on offline evaluations of the forward model, making it computationally cheap in practice compared to more sophisticated approaches. The method is illustrated with generic PDE and ODE models. It is then applied to synthetic and experimental electrophysiology measurements. In the second part of this thesis, we present a method to extract and select biomarkers from models outputs in view of performing classication tasks or solving parameter identification problems. The method relies on the resolution of a sparse optimization problem. The method is illustrated with simple models and then applied to synthetic measurements, including electrocardiogram recordings, and to experimental data obtained from micro-electrode array measurements