No description available.

The electrical activity recorded from the human colon could play an important role in analyzing the pattern of contractions under different physiologic or experimental states. In general, the frequency of the electrical activity is extremely irregular and time-varying. Its analysis requires a technique that considers variations in both time and frequency domains. The research undertaken was to analyze time-frequency variations of the human colonic electrical activity, to implement positive time- frequency distribution techniques in a computer system and to analyze theoretical signals using this technique to characterize a kernel function. Our results show that the uncertainty coefficient together with the marginal conditions and the average of the conditional PTFD in time and also in frequency can be applied to determine which kernel function and c-value were appropriate for calculating the PTFD of a sinusoidal signal. The selected kernel function constituted a comparative template of signals with similar characteristics. We found that those results were useful in analyzing the time- frequency variations of the electrical activity recorded in the human colon. The comparison of relative contributions of frequency bands showed that the band with the highest values during the pre- and interprandial period was 30-40 cpm suggesting an important role in the generation of bursts of these signals. The numerical results suggested that a meal can induce changes in the relative importance of frequencies below 10 cpm and a significant change in the 30-40 cpm band. In addition, a computer program of the Chakravarti method was implemented to calculate the Fourier transform of nonperiodical signals. This program was part of the computer program system developed to compute the PTFD of theoretical and experimental signals. / Thesis / Master of Engineering (MEngr)

No description available.

<p> An electronic circuit based on a modified version of the four branch Hodgkin-Huxley electrical equivalent circuit (Roy, 1972) has been proposed and implemented to simulate the pattern of the electrical activities present in the muscle cells of the mammalian small intestine. </p> <p> The analog's implementation comprises two main circuits to simulate these activities. One of them is concerned with generating sub threshold oscillations, while the other is basically a spike-generator circuit. Additional circuitry is included to interface them. Furthermore, the analog provides a parameter set by means of which its performance may be varied. Such settings may alter the intrinsic frequency, the magnitude of the depolarizing phase of the control potential for the response activity to occur, and also the frequency of the electrical response activity. </p> <p> Four such electronic oscillators, having different intrinsic frequencies, were coupled together in a chain structure with passive elements to simulate "frequency pulling" and "entrainment" . The model qualitatively reproduced the observed pattern of electrical activities in the small intestine. </p> / Thesis / Master of Engineering (MEngr)

Throughout neuronal development, bouts of spontaneous electrical activity are critical for the proper wiring of neuronal connections. Alterations in firing activity can affect growth cones, which tip developing and regenerating neurites and are responsible for the integration of extracellular guidance cues into pathfinding behaviors. While growing evidence implicates gaseous signaling molecules, nitric oxide (NO) and carbon monoxide (CO), as modulators of neuronal firing activity, less is understood about how they affect growth cone motility. Therefore, in this dissertation, I focus on how NO and CO affect electrical activity of developing and regenerating neurons and how these effects translate into changes at the growth cone level. The specific goals of this dissertation were to investigate 1) the neuron-type-specific effects of NO on growth cone motility; 2) the role of CO in the regulation of neuronal firing activity and excitability; and 3) the role CO plays in the regulation of growth cone motility. Using the well-established developmental model, Helisoma trivolvis, neurons were isolated in single-cell culture allowing for the maximal control over environmental conditions for the direct characterization of NO and CO. In the study of NO, differences in B5 and B19 growth cone responses to NO were due to neuron-type-specific differences in action potential duration. Moreover, the non-responsive B19 growth cones could be made responsive to NO treatment upon the pharmacological broadening of its action potentials. While NO has been found to increase firing activity, the study of CO revealed that CO had the opposite effect on electrical activity, silencing spontaneous firing activity and decreasing neuronal excitability. The study of CO on growth cone motility showed that CO increased growth cone filopodial length through a soluble guanylyl cyclase/protein kinase G/ryanodine receptor mediated pathway without inducing robust increases in growth cone calcium concentration. Taken together, this dissertation reveals new insight into how NO and CO regulate electrical activity and growth cone motility, providing evidence for these gases as important signaling messengers during for the development and regeneration of nervous system.

Electrical activity of the stomach is one determining factor of gastric motility by controlling and coordinating contractions of the gastric musculature. These contractions, both tonic and phasic, are responsible for the storing, mixing, and emptying of food. Gastric electrical activity is therefore a very important factor for normal stomach function. The development of a multi-channel, bandlimited, signal amplifier and recording system, provides a means to record this electrical activity. Many practical issues are addressed to provide a signal of acceptable quality and several basic signal processing techniques are applied to increase the quality of these signals and provide extraction of important information regarding power and frequency content. Gastric electrical activity is recorded from the stomachs of several rats in various experiments. The recorded activity in different regions of the stomach, responsible for different functions, is compared and evaluated with respect to known cellular events. By introducing several stimuli and observing changes in recorded activity, the nervous control of the stomach via mediation of the electrical activity is also examined and modeled briefly. / Thesis / Master of Engineering (ME)

This thesis consists in the study of a periodically forced slow-fast system in both its excitable and oscillatory regimes. The slow-fast system under consideration is the FitzHugh-Nagumo model, and the periodic forcing consists of a train of Gaussian-shaped pulses, the width of which is much shorter than the action potential duration. This system is a qualitative model for both an excitable cell and a spontaneously beating cell submitted to periodic electrical stimulation. Such a configuration has often been studied in cardiac electrophysiology, due to the fact that it constitutes a simplified model of the situation of a cardiac cell in the intact heart, and might therefore contribute to the understanding of cardiac arrhythmias. Using continuation methods (AUTO software), we compute periodic-solution branches for the periodically forced system, taking the stimulation period as bifurcation parameter. We then study the evolution of the resulting bifurcation diagram as the stimulation amplitude is raised. In both the excitable and the oscillatory regimes, we find that a critical amplitude of stimulation exists below which the behaviour of the system is trivial: in the excitable case, the bifurcation diagram is restricted to a stable subthreshold period-1 branch, and in the oscillatory case, all the stable periodic solutions belong to isolated loops (i.e., to distinct closed solution branches). Due to the slow-fast nature of the system, the changes that take place in the bifurcation diagram as the critical amplitude is crossed are drastic, while the way the bifurcation diagram re-simplifies above some second amplitude is much more gentle. In the oscillatory case, we show that the critical amplitude is also the amplitude at which the topology of phase-resetting changes type. We explain the origin of this coincidence by considering a one-dimensional discrete map of the circle derived from the phase-resetting curve of the oscillator (the phase-resetting map), map which constitutes a good approximation of the original differential equations under certain conditions. We show that the bifurcation diagram of any such circle map, where the bifurcation parameter appears only in an additive fashion, is always characterized by the period-1 solutions belonging to isolated loops when the topological degree of the map is one, while these period-1 solutions belong to a unique branch when the topological degree of the map is zero.

This study examined the brain electrical activity of normal speakers in a non-delayed auditory feedback (DAF) condition and when experiencing DAF to determine the effect DAF would have on the Bereitschaftspotential (BP). The BP reflects the preparatory state of a person prior to motor execution of an act and can be observed 1500 to 500 ms prior to voluntary movement. The participants in the study included 10 adults with normal speech. Each read a series of 30 sentences, both without DAF and with DAF, while the BP was measured. Results indicate that the BP is present across the scalp in both the control condition and the DAF condition; however, the BP is reduced in the DAF condition. The scalp distribution maps indicate an increased negativity in the left frontal lobe in the DAF condition. These findings suggest that while the brain is engaged in processing current information that has already been initiated, the motor system may not be able to be primed for the next sequential motor event. There is still a need for more research to explore the motor control of speech and the ways altered feedback may disrupt the speech motor control.

京都大学 / 新制・論文博士 / 博士(医学) / 乙第13580号 / 論医博第2302号 / 新制||医||1069(附属図書館) / (主査)教授 平井 豊博, 教授 江木 盛時, 教授 齋藤 潤 / 学位規則第4条第2項該当 / Doctor of Medical Science / Kyoto University / DFAM

L’accouchement prématuré est l’un des problèmes majeurs en obstétrique. Par suite, il a été un sujet d'intérêt pour de nombreux chercheurs. Parmi les nombreuses méthodes utilisées pour enregistrer la contractilité utérine, le plus utilisé est l'EHG abdominal, comme étant un outil facile à utiliser et non invasif. De nombreuses études ont indiqué que l'utilisation de ce signal pourrait être un outil très puissant pour surveiller la grossesse et pour détecter le travail. Il permet en effet d'accéder à l'utérus ainsi que la synchronisation de l'activité utérine, en utilisant des signaux multiples. Il a été démontré que l'analyse de connectivité des signaux EHG a donné des résultats prometteurs en application clinique, comme la classification des contractions de travail et de grossesse. Cependant, dans presque toutes les études antérieures, les matrices de corrélation EHG étaient souvent réduites en ne gardant que leur moyenne et les écarts-types, ce qui a peut aboutir à perdre des informations pertinentes en raison de ce moyennage, ce qui peut induire le taux de classification relativement faible jusqu'à présent. Pour caractériser précisément la matrice de corrélation et quantifier la connectivité associée, nous avons proposé dans cette thèse d'utiliser une technique de mesure de réseau basée sur la théorie des graphes. Selon cette approche, la matrice de corrélation obtenue peut être représentée sous forme de graphiques constitués d'un ensemble de nœuds (électrodes) interconnectés par des arêtes (valeurs de connectivité / corrélation entre électrodes). La nouvelle procédure de l'analyse des signaux EHG enregistrés pendant la grossesse et le travail se base sur la caractérisation de la corrélation entre les activités électriques utérines et sur sa quantification précise en utilisant l'approche de la théorie des graphes. Le pipeline de traitement inclut i) l'estimation des dépendances statistiques entre les différents signaux EHG enregistrés, ii) la quantification des matrices de connectivité obtenues à l'aide de l'analyse théorique des graphes et iii) l'utilisation clinique des mesures de réseau pour la surveillance de la grossesse ainsi que la classification entre les éclosions d'EHG de grossesse et de travail. Une comparaison avec les paramètres déjà existants utilisés pour la détection du travail et la détection d’accouchement prématuré sera également effectuée. Nous étudions également une nouvelle méthode pour étudier la connectivité source EHG, afin de surmonter le problème du calcul de la connectivité au niveau de la surface abdominale. Les résultats de cette thèse montrent que cette approche basée sur la théorie de graphe est un outil très prometteur pour quantifier la synchronisation utérine, lorsqu'elle est appliquée à l'abdomen, pour une meilleure surveillance de la grossesse. Nous espérons que cette approche soit utilisée pour le suivi de la grossesse et contribuerait ainsi à la prédiction précoce de l’accouchement prématuré. / Preterm birth remains a major problem in obstetrics. Therefore, it has been a topic of interest for many researchers. Among the many methods used to record the uterine contractility, the most used is the abdominal EHG, as being an easy to use and a non-invasive tool. Many studies have reported that the use of this signal could be a very powerful tool to monitor pregnancy and to detect labor. It indeed permits to access the uterine as well as the synchronization of the uterine activity, by using multiple signals. It has been shown that the connectivity analysis gave promising results when using EHG recordings in clinical application, such as the classification labor/pregnancy contractions. However, in almost all previous studies EHG correlation matrices were often reduced keeping only their mean and standard deviations thus relevant information may have been missed due to this averaging, which may induce the relatively low classification rate reported so far. To characterize precisely the correlation matrix and quantify the associated connectivity, we proposed in this thesis to use a network measure technique based on graph theory. According to this approach, the obtained correlation matrix can be represented as graphs consisting of a set of nodes (electrodes) interconnected by edges (connectivity/correlation values between electrodes). The new framework, to analyze the EHG signals recorded during pregnancy and labor, is based on the characterization of the correlation between the uterine electrical activities and on its precise quantification by using graph theory approach. The processing pipeline includes i) the estimation of the statistical dependencies between the different recorded EHG signals, ii) the quantification of the obtained connectivity matrices using graph theory-based analysis and iii) the clinical use of network measures for pregnancy monitoring as well as for the classification between pregnancy and labor EHG bursts. A comparison with the already existing parameters used in the state of the art for labor detection and preterm labor prediction will also be performed. We also investigate a new method to study the EHG source connectivity, to overcome the problem of computing the connectivity at the abdominal surface level. The results of this thesis showed that this network-based approach is a very promising tool to quantify uterine synchronization, when applied at the abdominal level, for a better pregnancy monitoring. We expect this approach to be further used for the monitoring of pregnancy and would thus help for the early prediction of preterm labor.