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1
Ponce, Alvarez Adrián. "Probabilistic models for studying variability in single-neuron and neuronal ensemble activity." Thesis, Aix-Marseille 2, 2010. http://www.theses.fr/2010AIX20706.
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Une des caractéristiques les plus singulières de l’activité corticale est son degré élevé de variabilité. Ma thèse dedoctorat s’est focalisée sur l’étude de (i) l’irrégularité des intervalles entre potentiels d’action (PAs)successivement émis par un neurone, et (ii) la variabilité dans l’évolution temporelle de l’activité d’un ensemblede neurones. Premièrement, j’ai étudié l’irrégularité des neurones enregistrés dans le cortex moteur de singesmacaques performant une tâche d’estimation du temps et de préparation à l’action. J’ai montré que l’irrégularitén’est pas un paramètre libre de l’activité neuronale, contrairement au taux de PAs, mais est déterminée par lescontraintes structurelles des réseaux neuronaux. Deuxièmement, j’ai utilisé le modèle de Markov caché (MMC)pour analyser l’activité d’ensembles de neurones enregistrés dans plusieurs aires corticales, sensorielles etmotrices, de singes exécutant une tâche de discrimination tactile. J’ai montré que les processus sensoriels etdécisionnels sont distribués dans plusieurs aires corticales. Les résultats suggèrent que l’action et la décision surlaquelle elle est basée sont reliées par une cascade d’évènements non stationnaires et stochastiques. Finalement,j’ai utilisé le MMC pour caractériser l’activité spontanée d’un ensemble de neurones du cortex préfrontal d’unrat. Les résultats montrèrent que l’alternance entre les états UP et DOWN est un processus stochastique etdynamique. La variabilité apparaît donc aussi bien pendant l’activité spontanée que pendant le comportementactif et semble être contrainte par des facteurs structurels qui, à leur tour, contraignent le mode d’opération desréseaux neuronauxA hallmark of cortical activity is its high degree of variability. The present work focused on (i) the variability ofintervals between spikes that single neurons emit, called spike time irregularity (STI), and (ii) the variability inthe temporal evolution of the collective neuronal activity. First, I studied the STI of macaque motor corticalneurons during time estimation and movement preparation. I found that although the firing rate of the neuronstransmitted information about these processes, the STI of a neuron is not flexible and is determined by thebalance of excitatory and inhibitory inputs. These results were obtained by means of an irregularity measure thatI compared to other existing measures. Second, I analyzed the neuronal ensemble activity of severalsomatosensory and motor cortical areas of macaques during tactile discrimination. I showed that ensembleactivity can be effectively described by the Hidden Markov Model (HMM). Both sensory and decision-makingprocesses were distributed across many areas. Moreover, I showed that decision-related changes in neuronalactivity rely on a noise-driven mechanism and that the maintenance of the decision relies on transient dynamics,subtending the conversion of a decision into an action. Third, I characterized the statistics of spontaneous UP andDOWN states in the prefrontal cortex of a rat, using the HMM. I showed that state alternation is stochastic andthe activity during UP states is dynamic. Hence, variability is prominent both during active behavior andspontaneous activity and is determined by structural factors, thus rending it inherent to cortical organization andshaping the function of neural networks
2
Sitnikov, Sergey. "Activity dependent neuron-glia interactions in health and disease." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708663.
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Hanna, Brian Dale. "Control of sympathetic neuron and cardiovascular effector activity by carbon dioxide." Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75884.
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The effect of CO$ sb2$ on sympathetic preganglionic neuron (SPN) activity and hindlimb neurogenic vascular resistance (HVR) was investigated in cats. Both variables increased as continuous functions of systemic arterial PCO$ sb2$, from hypocapnia to hypercapnia. Eucapnic PCO$ sb2$ was responsible for a significant component of SPN background activity and HVR. The carotid body chemoreceptors were shown to contribute to the CO$ sb2$ response of SPNs, since section of the carotid sinus nerves, after prior section of the aortic nerves, reduced the CO$ sb2$ response of SPNs. A significant ventral medullary contribution to this CO$ sb2$ relationship was demonstrated, since the CO$ sb2$ response persisted after peripheral chemodenervation, was lost after acute spinal transsection and was markedly attenuated by cold-block of either the entire exposed ventral surface of the medulla or the specific bilateral area "S". Superficial ventral medullary chemoreceptor involvement was confirmed, since changes in HVR, comparable to those caused by altering arterial PCO$ sb2$, occurred with changes in the (H$ sp+$) and PCO$ sb2$ in artificial CSF perfusing these structures.
4
Spencer, Robert Michael. "Rhythmic motor system control by projection neuron activity pattern and rate." Miami University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=miami1461269867.
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Soofi, Wafa Ahmed. "Regulation of rhythmic activity in the stomatogastric ganglion of decapod crustaceans." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53440.
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Neuronal networks produce reliable functional output throughout the lifespan of an animal despite ceaseless molecular turnover and a constantly changing environment. The cellular and molecular mechanisms underlying the ability of these networks to maintain functional stability remain poorly understood. Central pattern generating circuits produce a stable, predictable rhythm, making them ideal candidates for studying mechanisms of activity maintenance. By identifying and characterizing the regulators of activity in small neuronal circuits, we not only obtain a clearer understanding of how neural activity is generated, but also arm ourselves with knowledge that may eventually be used to improve medical care for patients whose normal nervous system activity has been disrupted through trauma or disease. We utilize the pattern-generating pyloric circuit in the crustacean stomatogastric nervous system to investigate the general scientific question: How are specific aspects of rhythmic activity regulated in a small neuronal network?
The first aim of this thesis poses this question in the context of a single neuron. We used a single-compartment model neuron database to investigate whether co-regulation of ionic conductances supports the maintenance of spike phase in rhythmically bursting “pacemaker” neurons. The second aim of the project extends the question to a network context. Through a combination of computational and electrophysiology studies, we investigated how the intrinsic membrane conductances of the pacemaker neuron influence its response to synaptic input within the framework of the Phase Resetting Curve (PRC). The third aim of the project further extends the question to a systems-level context. We examined how ambient temperatures affect the stability of the pyloric rhythm in the intact, behaving animal. The results of this work have furthered our understanding of the principles underlying the long-term stability of neuronal network function.
6
Rüppell, Maximilian Alexander [Verfasser], and Ulrich [Akademischer Betreuer] Egert. "Single neuron dynamics and interaction in neuronal networks during synchronized spontaneous activity." Freiburg : Universität, 2019. http://d-nb.info/1237617685/34.
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Mitelut, Catalin C. "Characterizing single neuron activity patterns and dynamics using multi-scale spontaneous neuronal activity recordings of cat and mouse cortex." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/63570.
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Throughout most of the 20th century the brain has been studied as a reflexive system with ever improving recording methods being applied within a variety of sensory and behavioural paradigms.
Yet the brains of most animals (and all mammals) are spontaneously active with incoming sensory stimuli modulating rather than driving neural activity.
The aim of this thesis is to characterize spontaneous neural activity across multiple temporal and spatial scales relying on biophysical simulations, experiments and analysis of recordings from the visual cortex of cats and dorsal cortex and thalamus of mouse.
Biophysically detailed simulations yielded novel datasets for testing spike sorting algorithms which are critical for isolating single neuron activity. Sorting algorithms tested provided low error rates with operator skill being as important as sorting suite. Simulated datasets have similar characteristics to in vivo acquired data and ongoing larger-scope efforts are proposed for developing the next generation of spike sorting algorithms and extracellular probes.
Single neuron spontaneous activity was correlated to dorsal cortex neural activity in mice. Spike-triggered-maps revealed that spontaneously firing cortical neurons were co-activated with homotopic and mono-synaptically connected cortical areas, whereas thalamic neurons co-activated
with more diversely connected areas. Both bursting and tonic firing modes yielded similar maps and the time courses of spike-triggered-maps revealed distinct patterns suggesting such dynamics may constitute intrinsic single neuron properties. The mapping technique extends previous work to
further link spontaneous neural activity across temporal and spatial scales and suggests additional avenues of investigation.
Synchronized state cat visual and mouse sensory cortex electrophysiological recordings revealed that spontaneously occurring activity UP-state transitions fall into stereotyped classes of events that can be grouped. Single visual cortex neurons active during UP-state transitions fire in a partially preserved order extending previous findings on high firing rate neurons in rat somatosensory and auditory cortex. The firing order for many neurons changes over periods longer than 30-minutes suggesting a complex non-stationary temporal neural code may underlie spontaneous and stimulus
evoked neural activity.
This thesis shows that ongoing spontaneous brain activity contains substantial structure that can be used to further our understanding of brain function.Medicine, Faculty of
Graduate
8
Haase, Stephanie Jean. "Exploring the relationship between circadian neuron activity patterns and behavioral output in Drosophila." Diss., University of Iowa, 2019. https://ir.uiowa.edu/etd/6754.
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Circadian clocks drive the daily patterns of behavior and physiology observed in most organisms. These internal clocks allow organisms to advantageously align their behavior to daily cycles in the environment such as light and temperature. The fruit fly Drosophila displays many robust, daily behavioral rhythms including discrete bouts of locomotor activity at dawn (i.e. morning activity) and dusk (i.e. evening activity). The molecular clocks that drive these daily activity bouts are found in approximately 150 circadian pacemaker neurons in the fly brain. Interestingly, the timing of the molecular clocks is synchronous between all pacemaker neurons, yet different subsets of these neurons appear to make quite different contributions to the regulation of morning vs. evening activity. It remains poorly understood how the molecular circadian clock drives daily rhythms in pacemaker neuron activity or how the activities of different groups of pacemaker neurons combine to produce complex behavioral output.
The overall goal of this thesis is to characterize how different subsets of Drosophila pacemaker neurons contribute to daily behavioral regulation both individually and as a network. To examine daily patterns of neuronal activity in different groups of circadian clock neurons, we have established imaging methods using genetically encoded fluorescent sensors. For these sensors, changes in fluorescence levels correspond to changes in neuronal activity, thus allowing us to measure neuronal activity patterns in real-time and throughout the day. Using these tools, I have characterized the daily activity patterns of different groups of the clock neurons that agree with published rhythms in activity as assessed by patch-clamp electrophysiology and calcium imaging
We have also used genetic and molecular approaches such as RNA interference (RNAi) to alter gene expression in a tissue-specific manner. These approaches allow us to manipulate the function of different groups of clock neurons and to determine how these manipulations affect rhythmic behavior and neuronal activity patterns. We have silenced different subsets of circadian pacemaker neurons using RNAi knockdown of the NARROW ABDOMEN (NA) sodium leak channel and identified a complex role for a subset of the posterior dorsal neurons 1 (DN1p) in regulating locomotor behavior. The DN1p are known to be involved in promoting morning behavior, and recent studies have shown that a subset of the DN1p regulate midday sleep bouts via downstream sleep regulating neurons. Our data suggest that the DN1p neurons likely suppress midday activity through inhibition of other circadian pacemaker neurons, and that this inhibitory role can be compensated for by light.
Finally, we have also examined the intracellular mechanisms regulating circadian neuronal output. Rhythmic activity of the NA leak channel and its mammalian ortholog (NALCN) have been shown to contribute to daily excitability rhythms in circadian pacemaker neurons. We used temporally-restricted expression of RNAi and rescue constructs to identify a developmental requirement for the NA channel complex in Drosophila, and we demonstrate that channel complex proteins are very stable in the Drosophila brain. These data suggest that circadian regulation of the NA channel in adults may involve post-translational mechanisms that control activity and not just expression of the channel complex.
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Cherry, Cortnie Lauren. "Mechanisms of Depolarization Induced Dendritic Growth of Drosophila Motor Neurons." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/195475.
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MECHANISMS OF DEPOLARIZATION INDUCED DENDRITIC GROWTH OF DROSOPHILA MOTOR NEURONS Cortnie Lauren Cherry The University of Arizona, 2006 Director: Richard B. Levine The study of the cellular mechanisms underlying dendritic growth contributes to our understanding of nervous system development, function and disease. Electrical activity is a fundamental property of neurons, and this property is utilized to influence the mechanisms involved in dendrite formation and maturation. Here we employ the Drosophila transgenic system to quantify dendritic growth of identified motor neurons using both in vitro and in vivo techniques. Two novel techniques are introduced: one a system to visualize and measure dendritic outgrowth in cultured neurons using reporter proteins, and the other using 3D reconstruction to measure the arborization of identified motor neurons in vivo. Both transgenic manipulation of K+ channel function and depolarizing concentrations of K+ in the culture medium result in an acceleration of dendritic outgrowth. Depolarization induced outgrowth is dependent on Plectreurys Toxin (PLTX)-sensitive voltage-gated calcium current and protein synthesis in cultured motor neurons. Depolarization leads to direct induction of fos, a protein that heterodimerizes with jun to make the functional transcription factor, AP-1. Fos, but not jun, is necessary for basal levels of dendritic growth, while both are necessary for depolarization induced outgrowth. Over-expression of AP-1 in control cells is sufficient to cause dendritic outgrowth. The transcription factor Adf-1 is also necessary for basal and depolarization induced growth, but unlike AP-1 is not sufficient to cause outgrowth when over-expressed. Another transcription factor CREB, on the other hand, is not necessary for basal levels of dendritic growth, but is necessary for depolarization induced dendritic growth. Over-expression of CREB, like Adf-1, is not sufficient to cause dendritic outgrowth. These findings present exciting new techniques for the study of the field of dendritic regulation and contribute to our understanding of the cellular mechanisms underlying dendritic growth.
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Karameh, Fadi Nabih. "A model for cerebral cortical neuron group electric activity and its implications for cerebral function." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/27110.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.Includes bibliographical references (p. 245-265).
The electroencephalogram, or EEG, is a recording of the field potential generated by the electric activity of neuronal populations of the brain. Its utility has long been recognized as a monitor which reflects the vigilance states of the brain, such as arousal, drowsiness, and sleep stages. Moreover, it is used to detect pathological conditions such as seizures, to calibrate drug action during anesthesia, and to understand cognitive task signatures in healthy and abnormal subjects. Being an aggregate measure of neural activity, understanding the neural origins of EEG oscillations has been limited. With the advent of recording techniques, however, and as an influx of experimental evidence on cellular and network properties of the neocortex has become available, a closer look into the neuronal mechanisms for EEG generation is warranted. Accordingly, we introduce an effective neuronal skeleton circuit at a neuronal group level which could reproduce basic EEG-observable slow (< 15 Hz) oscillatory phenomenon. The circuit incorporates basic laminar organization principles of the cortex. Interaction between neuronal groups is defined on three scales, namely the columnar (0.3mm), columnar assembly (1-2mm) and areal (> 3mm). The effective circuit makes use of the dynamic properties of the layer 5 network to explain intra-cortically generated augmenting responses, restful alpha, slow wave (< 1Hz) oscillations, and disinhibition-induced seizures. Based on recent cellular evidence, we propose a hierarchical binding mechanism in tufted layer 5 cells which acts as a controlled gate between local cortical activity and inputs arriving from distant cortical areas. This gate is manifested by the switch in output firing patterns in tufted
(cont.) layer 5 cells between burst firing and regular spiking, with specific implications on local functional connectivity. This hypothesized mechanism provides an explanation of different alpha band (10Hz) oscillations observed recently under cognitive states. In particular, evoked alpha rhythms, which occur transiently after an input stimulus, could account for initial reogranization of local neural activity based on (mis)match between driving inputs and modulatory feedback of higher order cortical structures, or internal expectations. Emitted alpha rhythms, on the other hand, is an example of extreme attention where dominance of higher order control inputs could drive reorganization of local cortical activity. Finally, the model makes predictions on the role of burst firing patterns in tufted layer 5 cells in redefining local cortical dynamics, based on internal representations, as a prelude to high frequency oscillations observed in various sensory systems during cognition.
by Fadi Nabih Karameh.
Ph.D.
11
Shao, Jie. "Putative Role of Connectivity in the Generation of Spontaneous Bursting Activity in an Excitatory Neuron Population." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5086.
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Population-wide synchronized rhythmic bursts of electrical activity are present in a
variety of neural circuits. The proposed general mechanisms for
rhythmogenesis are often attributed to intrinsic and synaptic properties. For example,
the recurrent excitation through excitatory synaptic connections determines
burst initiation, and the slower kinetics of ionic currents or synaptic depression
results in burst termination. In such theories, a slow recovery process is essential
for the slow dynamics associated with bursting.
This thesis presents a new hypothesis that depends on
the connectivity pattern among neurons rather than a slow kinetic process to achieve
the network-wide bursting. The thesis
begins with an introduction of bursts of electrical activity in a purely excitatory
neural network and existing theories explaining this phenomenon. It then covers
the small-world approach, which is applied to modify the network structure in the simulation,
and the Morris-Lecar (ML) neuron model, which is used as the component cells in the network.
Simulation results of the dependence of bursting activity on network connectivity,
as well as the inherent network properties explaining this dependence are described.
This work shows that the network-wide bursting activity emerges in the small-world network
regime but not in the regular or random networks, and this small-world bursting primarily results
from the uniform random distribution of long-range connections in the network, as well as
the unique dynamics in the ML model. Both attributes foster progressive synchronization in
firing activity throughout the network during a burst, and this synchronization may terminate a burst in the absence of an obvious slow recovery process. The thesis concludes with possible future work.
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Kaur, Pareena, and Pareena Kaur. "Development of an In-Vivo Model to Record Motor Neuron Activity in the Awake, Behaving Rat." Thesis, The University of Arizona, 2017. http://hdl.handle.net/10150/625019.
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The purpose of this study was to develop an in-vivo model to record motor neuron (MN) activity in the awake, behaving rat. This model is necessary for subsequent studies in which specific ion channels, thought to regulate MN activity, will be blocked pharmacologically while rats perform voluntary motor tasks. Rats were comfortably secured in an apparatus with their hind paw connected to a force transducer. Using operant conditions, they were trained to make controlled, voluntary contractions of the tibialis anterior, an ankle dorsiflexor. Once trained, activity was successfully recorded during the voluntary task from 20 motor units in 2 rats using intramuscular microelectrodes. The average firing rate of these units was 54 ± 12 impulses/s, substantially higher than equivalent recordings made from human biceps brachii muscle (14.8 ± 2 impulses/s). Therefore, this system provides a working in-vivo model for recording motor neuron activity in the awake, behaving rat that can be used for numerous studies in the future.
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Wilson, David Ian Greig. "An investigation into the function of single-neuron activity in the mesoaccumbens dopamine system of the rat." Thesis, University of St Andrews, 2005. http://hdl.handle.net/10023/2828.
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The mesoaccumbens dopamine system has been implicated in many basic psychological processes (e.g. "wanting" and "liking") and illnesses (e.g. addiction, depression, schizophrenia). However, the precise computational functions of nucleus accumbens and dopamine neurons within the system remain unknown. In this thesis, we test some of the current hypotheses regarding the function of this system using a behavioural neurophysiology approach in the rat. The first question we wanted to answer was whether nucleus accumbens neurons process reward-predictive stimuli (e.g. conditioned reinforcers) and reward delivery differently, since previous studies report equivocal findings. To do so, we trained thirsty rats to bar-press on a second-order schedule of saccharin reinforcement, within which the temporal pattern of rats' bar-pressing was reinforced by presentations of a conditioned reinforcer and primary reinforcer (reward). We found that nucleus accumbens neurons typically responded to these conditioned and primary reinforcers with opposite sign, which suggests they were processed differently. We were not sure whether responses to conditioned reinforcers encoded reward-prediction or facilitated a behavioural switch in the rat's behaviour. Indeed, since studies using a variety of experimental techniques have implicated the mesoaccumbens dopamine system in both reward prediction and behavioural switching, we sought to test whether neurons in the nucleus accumbens and dopamine-rich areas of the midbrain respond to outcome-associated stimuli to predict reward or switch behaviour. We found both sets of neurons predominantly did the former. Finally, to understand more about reward consummatory responses from both sets of neurons, we developed a rat behavioural task providing measures of reward "wanting" and "liking". In conclusion, on the basis of our data, the most parsimonious explanation for the function of the mesoaccumbens dopamine system is that it acts to modulate goal-seeking behaviour. Further research is required to identify the function of the interactions between nucleus accumbens and dopamine neurons during goal-seeking and goal consumption.
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Radecki, Guillaume. "Imagerie cellulaire par résonance magnétique rehaussée au manganèse (CelMEMRI)." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112212/document.
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La science a avancé depuis le XIX ème siècle. Des nouveaux outils sont apparus : la microscopie optique nous donne la vision des cellules, la microscopie électronique nous entraine au cœur de celles-ci. L’imagerie par résonance magnétique est apparue dans les années soixante-dix. Depuis son évolution, l’IRM nous entraine de plus en plus loin dans les profondeurs secrètes de nos cerveaux. La possibilité d’observer l’activité neuronale à l’aide de l’imagerie fonctionnelle est une grande révolution. Cette thèse montrera la possibilité que l’on a d’observer l’activité d’un neurone individuel sans modification de son réseau grâce à l’imagerie rehaussée au manganèse. L’étude sera effectuée sur des Aplysies à très haut champ (17T). Ces animaux sont des mollusques marins gastropodes qui possèdent une particularité : leurs neurones sont de tailles importantes, ils peuvent atteindre 1 mm de diamètre. Leurs neurones sont regroupés en plusieurs ganglions. Mon étude portera sur le ganglion buccal, qui est le ganglion le plus étudié dans les recherches en électrophysiologie. Avant de réaliser les acquisitions, j’ai dû concevoir plusieurs antennes de tailles microscopiques adaptées à la taille des ganglions. En réduisant la taille des antennes, le rapport signal sur bruit augmente. Dans un deuxième temps, une double antenne a été développée permettant l’acquisition de deux échantillons simultanément. Cette antenne a nécessité de créer des préamplificateurs fonctionnant à 730 MHz. La première série d’expériences a permis d’observer l’évolution de l’activité neuronale selon différents stimulus liés au comportement alimentaire des aplysies in-vivo. J’ai montré grâce à la technique mise en place que l’on peut distinguer par IRM l’activité de chaque neurone face à un stimulus. Par la suite, pour continuer ce travail, une deuxième série d’expériences a été effectuée in-vitro. J’ai étudié le comportement des neurones selon les neuro-stimulateurs perfusés : la dopamine et la sérotonine, tous les deux présents naturellement dans l’aplysie. Globalement les neurones ont été activés mais après les avoir observés individuellement, j’ai remarqué quelques différences selon les neurotransmetteurs. Cette technique peut maintenant être utilisée pour étudier d’autres conduites de l’aplysie comme le comportement compulsif. L’étude sur la mémoire peut être aussi envisagée. Les origines comportementales ont probablement des mécanismes identiques entre les différentes espèces animales et donc avec l’Homme comme l’a démontré les études d’Eric Kandel sur la mémoireScience has evolved since the 19th century. New tools have appeared such as optical microscopy which gives us the vision of cells and electronic microscopy which leads us into their hearts. The magnetic resonance imaging appeared in the seventies. Evolving over time, the MRI has taken us farther and farther into the secret depths of our brains. The possibility of observing the neuronal activity thanks to the functional imaging is a major evolution. This thesis will show the possibility we have to observe the activity of a single neuron without modification of its network thanks to the manganese enhanced magnetic resonance imaging technique. The study was done on the Aplysia at very high field magnet (17T). These animals are marine gastropod mollusks with a peculiarity: their neurons are of important size and can reach 1 mm in diameter. Their neurons are grouped into several ganglia. My study concerns the buccal ganglion which is the most studied ganglia in the research in electrophysiology. Before making any acquisitions, I had to conceive several microscopic coils adapted to the size of the ganglions. By reducing the size of the coils, the signal of the noise ratio increases. Then, a double coil allowing the simultaneous acquisition of two samples was built. This antenna required the construction of pre-amplifiers operating at 730 MHz. The first series of experiments helped observe the evolution of the neuronal activity according to different stimuli linked to the eating habits of the Aplysia in vivo. Thanks to the technique implemented, I shall show that, using MRI, it is possible to distinguish the activity of each neuron with respect to a stimulus. Afterwards, to continue this work, a second series of experiments was made in vitro. I studied the behavior of neurons when perfused with neural stimulators: dopamine and serotonin, both naturally present in the Aplysia. Generally, all neurons were activated but when observing them individually, I noticed some differences. Studies in electrophysiology will allow us to get a better understanding and a confirmation of the results of this study. The MEMRI technique can be used in the future to study various disorders such as compulsive behaviors, which are present in the Aplysia, and probably have the same origins as in humans, given that many fundamental processes (such as memory studied by Eric Kandel who he demonstrated that human and Aplysia memories works with the same mechanism) are similar between the two species
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Tong, Tong [Verfasser], and Trese [Akademischer Betreuer] Leinders-Zufall. "GnRH-induced spike activity and calcium signals in GnRHR neuron during female reproductive cycle / Tong Tong ; Betreuer: Trese Leinders-Zufall." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2017. http://d-nb.info/1141175991/34.
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Kruscha, Alexandra. "Information transmission by the synchronous activity of neuronal populations." Doctoral thesis, Humboldt-Universität zu Berlin, 2017. http://dx.doi.org/10.18452/18391.
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Sensorische Nervenzellen kodieren Informationen über die Umwelt mittels
elektrischer Impulse, sogenannte Aktionspotentiale oder Spikes. Diese werden
weitergeleitet zu postsynaptischen Neuronen im zentralen Nervensystem, welche
unterschiedliche Auslesestrategien verwenden. Integratorzellen summieren alle
ankommenden Aktionspotentiale auf, wodurch sie die Gesamtaktivität einer
präsynaptischen Population messen. Koinzidenzdetektoren hingegen, werden nur
durch das synchrone Feuern der zuführenden Neuronenpopulation aktiviert.
Die grundlegende Frage dieser Dissertation lautet: Welche Information eines
zeitabhängigen Signals kodieren die synchronen Spikes einer Neuronenpopulation
im Vergleich zu der Summe all ihrer Aktionspotentiale? Hierbei verwenden wir die
Theorie stochastischer Prozesse: wir berechnen Spektralmaße, die es ermöglichen
Aussagen darüber zu treffen welche Frequenzkomponenten eines Signals vorwiegend
transmittiert werden. Im Gegensatz zu früheren Studien, verstehen wir unter
einem synchronen Ereignis nicht zwangsläufig, dass die gesamte Population
simultan feuert, sondern, dass ein minimaler Anteil („Synchronizitätsschranke")
gleichzeitig aktiv ist. Unsere Analyse zeigt, dass die synchrone
Populationsaktivität als ein Bandpass-Informationsfilter agieren kann: die
synchronen Spikes kodieren hauptsächlich schnelle Signalanteile. Damit stellt
die Selektion simultaner Neuronenaktivität ein potentielles Mittel dar um
gleichzeitig anwesende, konkurrierende Signale voneinander zu trennen. Dabei
hängen die genauen Charakteristika der Informationsfilterung ausschlaggebend von
der Synchronizitätsschwelle ab. Insbesondere zeigt sich, dass eine Symmetrie in
der Schwelle vorliegt,die die Äquivalenz der Kodierungseigenschaften von
synchronem Feuern und synchronem Schweigen offenlegt. Unsere analytischen
Ergebnisse testen wir mittels numerischer Simulationen und vergleichen sie mit
Experimenten am schwach elektrischen Fisch.Populations of sensory neurons encode information about the environment into electrical pulses, so called action potentials or spikes. Neurons in the brain process these pulses further by using different readout strategies. Integrator cells sum up all incoming action potentials and are thus sensitive to the overall activity of a presynaptic population. Coincidence detectors, on the other hand, are activated by the synchronous firing of the afferent population. The main question of this thesis is: What information about a common time-dependent stimulus is encoded in the synchronous spikes of a neuronal population in comparison to the sum of all spikes? We approach this question within the framework of spectral analysis of stochastic processes, which allows to assess which frequency components of a signal are predominantly encoded. Here, in contrast to earlier studies, a synchronous event does not necessarily mean that all neurons of the population fire simultaneously, but that at least a prescribed fraction ('synchrony threshold') needs to be active within a small time interval. We derive analytical expressions of the correlation statistics which are compared to numerical simulations and experiments on weakly electric fish. We show that the information transmission of the synchronous output depends highly on the synchrony threshold. We uncover a symmetry in the synchrony threshold, unveiling the similarity in the encoding capability of the common firing and the common silence of a population. Our results demonstrate that the synchronous output can act as a band-pass filter of information, i.e. it extracts predominantly fast components of a stimulus. If signals in different frequency regimes are concurrently present, the selection of synchronous firing events can thus be a tool to separate these signals.
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McKiernan, Erin Christy. "The role of specific voltage-activated and calcium-activated potassium currents in shaping motor neuron firing output during rhythmic motor activity." Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/145732.
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Rhythmic muscle contractions underlie a number of behaviors, such as respiration, ingestion, and locomotion, which are necessary for survival. Though in many cases motor neurons (MNs) themselves do not generate the basic motor rhythm, research suggests that the intrinsic properties of MNs may shape the timing of the final motor output. In particular, potassium (K⁺) currents can affect MN excitability and firing in a number of ways, including action potential repolarization, firing frequency, dendritic integration, repetitive firing, and burst termination. The roles played by K⁺ currents, therefore, make them ideal candidates to shape MN firing output during rhythmic activity. Just how crucial MN K⁺ currents are in shaping rhythmic motor output, which currents are crucial and what genes are responsible, and how these currents affect MN firing are areas of active investigation. Unfortunately, many previous studies attempting to answer such questions have relied on manipulations that affect large, and often unidentified, populations of neurons simultaneously. To effectively determine the role of MN currents in shaping rhythmic motor output we must target manipulations of specific ion channels to MNs. We used the Drosophila larval model system because the genetic tools available allow us to do just that. We targeted manipulations of specific calcium (Ca²⁺)-activated and voltageactivated K⁺ currents to identified populations of MNs. We hypothesized that MNs are not simply followers of network drive, but that MN firing output is further shaped during rhythmic motor activity by these K⁺ currents. Overall, our results show that though aspects of the motor output changed, such as burst duration, the system was remarkably robust in the face of K⁺ channel manipulations. Larvae expressing manipulations of the Ca²⁺-activated K⁺ channel, Slowpoke, and voltage-gated K⁺ channels Shal or eag/Shaker, continued to produce rhythmic motor output. Most manipulations had the strongest effect when expressed in cells other than just MNs, while restricting expression to smaller subsets of cells suggested that many of the effects were not intrinsic to the MNs. Even those manipulations which resulted in the strongest effects only changed burst or cycle durations by a few seconds, and did not affect the incidence or regularity of the rhythm. These results suggest that either these MN K⁺ currents minimally shape rhythmic motor output in this system, or compensation for the loss of K⁺ currents occurred. In sum, this work sheds light on the role of K⁺ currents in MNs during rhythmic activity, and points to a number of future directions examining the role of compensation in maintaining crucial rhythmic motor behaviors.
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Flood, Thomas F. "Identification of a Command Neuron Directing the Expression of Feeding Behavior in Drosophila melanogaster: A Dissertation." eScholarship@UMMS, 2011. https://escholarship.umassmed.edu/gsbs_diss/523.
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Feeding is one of the most important behaviors for an animal’s survival. At a gross level, it is known that the nervous system plays a major role in the expression of this complex behavior, yet a detailed understanding of the neural circuits directing feeding behavior remains unknown. Here we identify a command neuron in Drosophila melanogaster whose artificial activation, using dTrpA1, a heat-activated cation channel, induces the appearance of complete feeding behavior. We use behavioral, genetic, cellular and optical imaging techniques to show that the induced behavior is composed of multiple motor programs and can function to uptake exogenous, even noxious, material. Furthermore, we resolve the neuron’s location to the subesophageal ganglion, characterize its pre and post-synaptic sites, and determine its responsiveness to sucrose stimulation. Interestingly, the neuron’s dendritic field is proximal to sweet sensing axon terminals and its baseline activity corresponds to the fly’s satiation state, suggesting a potential point of integration between sensory, motor and motivational systems. The identification of a command neuron for feeding in a genetically tractable organism provides a useful model to develop a deeper understanding of the neural control of this ubiquitous and evolutionarily ancient behavior.
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Trauchessec, Vincent. "Local magnetic detection and stimulation of neuronal activity." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS301/document.
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L’activité cérébrale se traduit par des courants ioniques circulant dans le réseau neuronal.La compréhension des mécanismes cérébraux implique de sonder ces courants, via des mesures électriques ou magnétiques, couvrant différentes échelles spatiales. A l’échelle cellulaire, les techniques d’électrophysiologie sont maitrisées depuis plusieurs décennies, mais il n’existe pas actuellement d’outils de mesure locale des champs magnétiques engendrés par les courants ioniques au sein du réseau neuronal. La magnéto-encéphalographie(MEG) utilise des SQUIDs(Superconducting QUantum Interference Devices)fonctionnant à très basse température, placés en surface du crâne, qui fournissent une cartographie des champs magnétiques mais dont la résolution spatiale est limitée du fait de la distance séparant les capteurs des cellules actives. Le travail présenté dans cette thèse propose de développer des capteurs magnétiques à la fois suffisamment sensibles pour être capable de détecter le champ magnétique extrêmement faible générés par les courants neuronaux (de l’ordre de 10⁻⁹ T), et dont la géométrie est adaptable aux dimensions des cellules, tout en fonctionnant à température ambiante. Ces capteurs,basés sur l’effet quantique de magnétorésistance géante (GMR, sont suffisamment miniaturisables pour être déposés à l’extrémité de sondes d’une finesse de l’ordre de 100 μm. L’utilisation de capteurs GMR pour la mesure de signaux biomagnétiques fut d’abord testée lors d’expériences in-vitro, réalisées sur le muscle soléaire de souris. Ce système biologique a été choisi pour sa simplicité,rendant la modélisation accessible, ainsi que pour sa robustesse, permettant d’avoir des résultats fiables et reproductibles. Le parfait accord entre les prédictions théoriques et les signaux magnétiques mesurés valide cette technologie. Enfin, des expériences in vivo dans le cortex visuel du chat ont permis de réaliser la toute première mesure de la signature magnétique de potentiels d’action générés par des neurones corticaux, ouvrant la voie à la magnétophysiologieInformation transmission in the brain occurs through ionic currents flowing inside the neuronal network. Understanding how the brain operates requires probing this electrical activity by measuring the associated electric or magnetic field. At the cellular scale, electrophysiology techniques are well mastered, but there is no tool to perform magnetophysiology. Mapping brain activity through the magnetic field generated by neuronal communication is done via magnetoencephalography (MEG). This technique is based on SQUIDs (Superconducting Quantum Interference Devices) that operate at liquid Helium temperature. This parameter implies to avoid any contact with living tissue and a shielding system that increases the distance between the neurons and the sensors, limiting spatial resolution. This thesis work aims at providing a new tool to performmagnetic recordings at the neuronal scale. The sensors developed during this thesis are based on the Giant Magneto-Resistance (GMR) effect. Operating at room temperature, they can be miniaturize and shaped according to the experiment, while exhibiting a sensitivity that allows to measure amplitude of 10⁻⁹ T. Before targeting neurons, the use of GMR-based sensors for magnetic recordings of biological activity has been validated through invitro experiments on the mouse soleus muscle. This biological system has been chosen because of its simple organization, allowing for a realistic modelling, and for its robustness, in order to get reliable and replicable results. The perfect agreement between the measurements and the theoretical predictions represents a consistent validation of the GMR technology for biological applications. Then a specially adapted needle-shaped probe carrying micron-sized GMR sensors has been developed for in-vivo experiment in cat visual cortex. The very first magnetic signature of action potentials inside the neuropil has been measured, paving the way towards magnetophysiology
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Kordovan, Michael [Verfasser], and Stefan [Akademischer Betreuer] Rotter. "Constraints on neural activity imposed by the structure of neurons and networks." Freiburg : Universität, 2019. http://d-nb.info/1185391266/34.
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Weinreb, Alexis. "Impact de l’activité postsynaptique sur le développement et le maintien de la jonction neuromusculaire de C. elegans." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1137.
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Au cours du développement du système nerveux, l'activité des cibles post-synaptiques permet le raffinement du nombre et de la force des connexions neuronales. En employant la jonction neuromusculaire de Caenorhabditis elegans comme système modèle, nous avons étudié deux aspects de la mise en place de ces connexions. D'une part, nous montrons que le nombre de récepteurs présents à la jonction neuromusculaire est contrôlé par l'activité musculaire : une augmentation de l'activation synaptique entraîne une régulation différentielle des trois types de récepteurs présents à la jonction neuromusculaire. D'autre part, nous avons étudié les changements de la morphologie de certains motoneurones de la tête du ver, appelés neurones SAB, en fonction de l’activité musculaire. Une diminution de l’activité musculaire durant une période critique du développement entraîne une surcroissance axonale des neurones SAB. À travers différentes approches, nous avons pu identifier la suppression de la surcroissance axonale dans des mutants où la biosynthèse des neuropeptides est perturbée. Enfin, nous avons mis en évidence que la surcroissance axonale apparait également lors de perturbations plus générales de la physiologie cellulaire, telles qu'un choc thermique ou la surexpression d'un transgène, ce qui suggère que le système SAB est plastique et particulièrement sensible au cours du développementThroughout nervous system development, activity of the post-synaptic targets can regulate the connectivity of neural networks, affecting both the number and strength of synapses. Using the neuromuscular junction of Caenorhabditis elegans as a model system, we studied two processes displaying such plasticity. First, we show that the number of receptors present at the neuromuscular synapse is regulated by muscle activity: an increase in synaptic activity can lead to a differential regulation of the three types of receptors present at the neuromuscular junction. Second, we studied the activity-dependent morphological changes of one type of motor neurons in the worm’s head, called the SAB neurons. A decrease of muscle activity during a critical developmental phase leads to SAB axonal overgrowth. Using several approaches, we were able to observe suppression of SAB axonal overgrowth in mutants with a disruption of neuropeptides biosynthesis. Finally, we give evidence that axonal overgrowth also occurs following more general disruptions of cell physiology, such as a heat-shock or transgene overexpression, which suggest that the SAB system is plastic and sensitive during development
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Gómez, Orlandi Javier. "Noise, coherent activity and network structure in neuronal cultures." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/346925.
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In this thesis we apply a multidisciplinary approach, based on statistical physics and complex systems, to the study of neuronal dynamics. We focus on understanding, using theoretical and computational tools, how collective neuronal activity emerges in a controlled system, a neuronal culture. We show how the interplay between noise and network structure defines the emergent collective behavior of the system.
We build, using theory and simulation, a framework that takes carefully describes spontaneous activity in neuronal cultures by taking into account the underlying network structure of neuronal cultures and use an accurate, yet simple, model for the individual neuronal dynamics. We show that the collective behavior of young cultures is dominated by the nucleation and propagations of activity fronts (bursts) throughout the system. These bursts nucleate at specific sites of the culture, called nucleation points, which result in a highly heterogeneous probability distribution of nucleation. We are able to explain the nucleation mechanism theoretically as a mechanism of noise propagation and amplification called noise focusing.
We also explore the internal structure of activity avalanches by using well--defined regular networks, in which all the neurons have the same connectivity rules (motifs). Within these networks, we are able to associate to the avalanches an effective velocity and topological size and relate it to specific motifs. We also devise a continuum description of a neuronal culture at the mesoscale, i.e., we move away from the single neuron dynamics into a coarse--grained description that is able to capture most of the characteristic observables presented in previous chapters. This thesis also studies the spontaneous activity of neuronal cultures within the framework of quorum percolation. We study the effect of network structure within quorum percolation and propose a new model, called stochastic quorum percolation, that includes dynamics and the effect of internal noise.
Finally, we use tools from information theory, namely transfer entropy, to show how to reliably infer the connectivity of a neuronal network from its activity, and how to distinguish between different excitatory and inhibitory connections purely from the activity, with no prior knowledge of the different neuronal types. The technique works directly on the fluorescence traces obtained in calcium imaging experiments, without the need to infer the underlying spike trains.
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Chauvet, Pierre. "Sur la stabilité d'un réseau de neurones hiérarchique à propos de la coordination du mouvement." Angers, 1993. http://www.theses.fr/1993ANGE0011.
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Dans le premier chapitre, quelques réseaux de neurones capables d'apprendre des mouvements sont présentés. Un modèle du cortex cérébelleux, très impliqué dans la coordination des mouvements, est décrit en détail : c'est un réseau hiérarchique de réseaux de neurones linéaires, appelés unités de Purkinje, qui respectent la connectivité réelle. Les poids synaptiques, en apprentissage, sont modifiés par une règle de covariance. L'étude de ce modèle a permis de définir de nouvelles règles d'apprentissage appelées règles d'apprentissage variationnelles. L'objectif de cette thèse est d'en étudier les conditions de validité pour des unités non linéaires et d'en déduire une explication sur la manière dont la coordination de mouvements est apprise. Dans le deuxième chapitre, une unité de Purkinje linéaire plus générale est analysée. Les notions d'apprentissage et de reconnaissance sont approfondies. Il est montre qu'en phase d'apprentissage, une unité linéaire converge et est stable au sens de Lyapunov, sous certaines conditions. Sous ces mêmes conditions, les règles variationnelles vues dans le chapitre précédent sont confirmées. Dans la première partie du troisième chapitre, il est supposé que les neurones de l'unité sont non linéaires. Sa stabilité au sens de Lyapunov est étudiée par linéarisation autour d'un point équilibre. Dans la seconde partie, des délais sont introduits à l'intérieur de l'unité entre certains neurones. Il en résulte que l'unité possède une dynamique interne. Les conditions de convergence de la sortie de l'unité sont alors déterminées. Finalement, les règles variationnelles sont confirmées sous certaines conditions pour cette unité non linéaire. Dans le quatrième chapitre, l'étude d'un réseau d'unités de Purkinje est entreprise. Après l'étude d'un réseau simple, des délais entre unités sont introduits. Des conditions de stabilité de réseaux d'unités non linéaires sont déterminées et des simulations numériques permettent de vérifier que les règles variationnelles sont bien suivies. Enfin, un exemple de coordination musculaire apprise par un réseau est donné.
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Van, Rheede Joram Jacob. "The emergence of visual responses in the developing retinotectal system in vivo." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:57cb9bff-a085-4ac4-b413-c29112eeb78e.
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Patterned neuronal activity driven by the sensory environment plays a key role in the development of precise synaptic connectivity in the brain. It is well established that the action potentials (‘spikes’) generated by individual neurons are crucial to this developmental process. A neuron’s spiking activity is jointly determined by its synaptic inputs and its intrinsic excitability. It is therefore important to ask how a neuron develops these attributes, and whether the emergence of spiking might itself be governed by activity-dependent processes. In this thesis, I address these questions in the retinotectal system of Xenopus laevis. First, I investigate the extent to which visuospatial information is available to the developing retinotectal system. I show that the eyes of developing Xenopus larvae are hyperopic at the onset of vision, but rapidly grow towards correct vision. Despite its imperfect optics, the Xenopus eye is able to generate spatially restricted activity on the retina, which is evident in the spatial structure of the receptive fields (RFs) of tectal neurons. Using a novel method to map the visually driven spiking output and synaptic inputs of the same tectal neuron in vivo, I show that neuronal spiking activity closely follows the spatiotemporal profile of glutamatergic inputs. Next, I characterise a population of neurons in the developing optic tectum that does not fire action potentials, despite receiving visually evoked glutamatergic and γ-aminobutyric acid (GABA)ergic synaptic inputs. A comparison of visually spiking and visually non-spiking neurons reveals that the principal reason these neurons are ‘silent’ is that they lack sufficient glutamatergic synaptic excitation. In the final section of the thesis, I investigate whether visually driven activity can play a role in the ‘unsilencing’ of these silent neurons. I show that non-spiking tectal neurons can be rapidly converted into spiking neurons through a visual conditioning protocol. This conversion is associated with a selective increase in glutamatergic input and implicates a novel, spike-independent form of synaptic potentiation. I provide evidence that this novel plasticity process is mediated by GABAergic inputs that are depolarising during early development, and can act in synergy with N-methyl-D-aspartate receptors (NMDARs) to strengthen immature glutamatergic synapses. Consistent with this, preventing the depolarising effects of GABA or blocking NMDARs abolished the activity-dependent unsilencing of tectal neurons. These results therefore support a model in which GABAergic and glutamatergic transmitter systems function synergistically to enable a neuron to recruit the synaptic excitation it needs to develop sensory-driven spiking activity. This represents a transition with important consequences for both the functional output and the activity-dependent development of a neuron.
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Guzulaitis, Robertas. "The organisation principles of spinal neural network: temporal integration of somatosensory input and distribution of network activity." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2013. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2013~D_20130925_093153-76748.
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Spinal cord integrates somatosensory information and generates coordinated motor responses. Temporal integration can be used for discrimination of important stimuli from noise. Here it is shown that temporal integration of somatosensory inputs in sub second time scale is possible without changes of intrinsic properties of motoneurons. The activity of premotor neurons increases during temporal integration and can be a mechanism for short term information storage in spinal cord. Suppression of motor activity after painful somatosensory stimulus is called cutaneous silent period. This motor suppression is well described in humans and used for diagnostics. However it is not known if the suppression of motor activity is due to inhibition of motoneurons or reduction of excitatory drive from premotor neurons. Here it is shown that motoneurons are inhibited during cutaneous silent period. Neural networks of spinal cord not only process somatosensory information but generate locomotion and reflexes too. It is accepted that neural networks controlling front and hind limb movements are located in cervical and lumbar enlargements respectfully. Here it is shown that thoracic segments of spinal cord contribute to hind limb movements as well. It means that neural network generating movements is much more widely distributed than previously thought.Nugaros smegenys gauna somatosensorinę informaciją, ją integruoja ir generuoja motorinius atsakus. Disertacijoje parodoma, kad somatosensorinių įėjimų viršsekundinė laikinė integracija nugaros smegenų neuronų tinkle vyksta ne dėl motorinių neuronų vidinių savybių kitimo. Laikinės integracijos metu padidėja priešmotorinių neuronų aktyvumas ir tai gali lemti informacijos apie somatosensorinį įėjimą saugojimą. Somatosensorinis tylos periodas – tai motorinio aktyvumo slopinimas po skausmingo stimulo. Jis plačiai aprašytas žmonėse, bei taikomas diagnostikoje. Nepaisant plataus taikymo, somatosensorinio tylos periodo mechanizmai nėra ištirti – nebuvo žinoma ar šis motorinio aktyvumo slopinimas vyksta slopinant motorinius neuronus, ar eliminuojant motorinių neuronų žadinimą. Disertacijoje parodoma, kad somatosensorinio tylos periodo metu motoriniai neuronai yra slopinami. Be somatosensorinės informacijos apdorojimo nugaros smegenų neuronų tinklai užtikrina judėjimo ir refleksų valdymą. Yra priimta, kad priekines ir užpakalines galūnes valdantys neuronų tinklai išsidėstę atitinkamai nugaros smegenų kaklinės ir strėnų sričių išplatėjimuose. Disertacijoje parodoma, kad ir krūtininiai nugaros smegenų segmentai prisideda prie užpakalinių galūnių motorinio aktyvumo generavimo. Tai leidžia manyti, kad neuronų tinklas generuojantis judesius yra išplitęs labiau, nei manyta iki šiol.
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Kuebler, Eric Stephen. "Harnessing the Variability of Neuronal Activity: From Single Neurons to Networks." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37855.
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Neurons and networks of the brain may use various strategies of computation to provide the neural substrate for sensation, perception, or cognition. To simplify the scenario, two of the most commonly cited neural codes are firing rate and temporal coding, whereby firing rates are typically measured over a longer duration of time (i.e., seconds or minutes), and temporal codes use shorter time windows (i.e., 1 to 100 ms). However, it is possible that neurons may use other strategies. Here, we highlight three methods of computation that neurons, or networks, of the brain may use to encode and/or decode incoming activity. First, we explain how single neurons of the brain can utilize a neuronal oscillation, specifically by employing a ‘spike-phase’ code wherein responses to stimuli have greater reliability, in turn increasing the ability to discriminate between stimuli. Our focus was to explore the limitations of spike-phase coding, including the assumptions of low firing rates and precise timing of action potentials. Second, we examined the ability of single neurons to track the onset of network bursting activity, namely ‘burst predictors’. In addition, we show that burst predictors were less susceptible to an in vitro model of neuronal stroke (i.e., excitotoxicity). Third, we discuss the possibility of distributed processing with neuronal networks of the brain. Specifically, we show experimental and computational evidence supporting the possibility that the population activity of cortical networks may be useful to downstream classification. Furthermore, we show that when network activity is highly variable across time, there is an increase in the ability to linearly separate the spiking activity of various networks. Overall, we use the results of both experimental and computational methods to highlight three strategies of computation that neurons and networks of the brain may employ.
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Hernández, Navarro Lluís. "Theoretical and experimental approaches for the initiation and propagation of activity in spatially embedded neuronal cultures." Doctoral thesis, Universitat de Barcelona, 2018. http://hdl.handle.net/10803/565905.
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Spatial embedding and inherited metric constraints are a fundamental trait of biological neuronal circuits. However their role in shaping connectivity and dynamics has been often disregarded, with models of neuronal networks paying much more attention to the distribution of connections in the quest for understanding network's behavior. In this thesis we aim at filling this gap by studying the importance of metric features in the complex connectivity- dynamics-noise interplay that shapes spontaneous neuronal activity.
This thesis combines experiments in rat dissociated neuronal cultures with theoretical analyses to better comprehend the relevance of spatial embedding. We developed a new theoretical model grounded on Ising Models to assess metric effects in neuronal cultures' behavior, and in the context of percolation approaches. Once metric effects were settled, we illustrated their relevance in shaping spontaneous activity by perturbing the structural connectivity blueprint of neuronal cultures. This was achieved by patterning the substrate where neurons grow, and by using topographical molds that dictated the connectivity of the network. Next, and since the initiation of bursting activity is governed in great manner by a complex amplification mechanism that involves metric correlations and noise, we focused on the metric-driven amplification of spontaneous single-neuron noise to derive an analytical model that predicts the frequency of bursting events in neuronal cultures. We then further investigated in an experimental context the contribution of noise to the observed activity patterns, and by implementing a moderate electrical stimulation protocol that increases the level of activity noise in cultures. Finally, the latter study was completed with experiments regarding the specific role of inhibition in neuronal networks, to provide a wider understanding of the mechanisms that govern the initiation and propagation of activity fronts in cortical cultures.L'objectiu d'aquesta tesis és investigar els mecanismes que generen l'activitat espontània i estimulada en xarxes neuronals, més concretament en cultius corticals dissociats, i fent un especial èmfasi en l’efecte de les correlacions mètriques. En aquest marc, l’activitat col·lectiva consisteix en episodis esporàdics de dispars quasi sincronitzats entre totes les neurones del cultiu, anomenats “esclats de xarxa”. Tres elements principals en determinen les característiques: connectivitat entre neurones, dinàmica intrínseca neuronal, i soroll (activacions neuronals aleatòries). La investigació s’ha centrat en cinc línies de recerca: l’estudi de correlacions mètriques en cultius neuronals; el desenvolupament d’un model teòric per descriure i predir l’esclat de xarxa; l’anàlisi de la propagació dels fronts d’activitat experimentals sota pertorbacions estructurals de la connectivitat del cultiu; l’estudi de l’efecte de la inhibició en la iniciació i propagació dels esclats ‘in vitro’; i l’estudi de la resposta experimental dels cultius sota una estimulació elèctrica moderada de baixa freqüència. En la primera línia de recerca hem comprovat que les correlacions mètriques dominen el comportament dinàmic del cultiu, fins al punt d’emmascarar la contribució de la distribució del nombre de connexions. En la segona línia hem desenvolupat un model analític que prediu semi- quantitativament la freqüència dels esclats observada experimentalment. La tercera línia s’ha centrat en l’efecte de pertorbacions estructurals en la connectivitat; la dinàmica resultant ha mostrat una gran riquesa en patrons d’activitat, esclats de xarxa a diferents escales, i propagació altament específica de cada cultiu. La quarta línia de recerca ha demostrat que les xarxes sense inhibició disminueixen la seva freqüència d’esclat respecte a les xarxes control, que la velocitat de propagació de l’activitat incrementa lleugerament quan s’ha bloquejat la inhibició, i que els punts on s’inicien ens esclats varien respecte als controls. I, finalment, la cinquena línia de recerca ha constatat que l’aplicació d’un camp elèctric feble augmenta el soroll d’activitat de la xarxa, generant un increment en la freqüència dels esclats de xarxa.
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Belloir, Tiphaine. "Dispositif électro-optique à base de cristaux liquides pour la détection de l'activité neuronale in vitro." Thesis, Université Grenoble Alpes (ComUE), 2018. https://thares.univ-grenoble-alpes.fr/2018GREAT122.pdf.
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Les réseaux de neurones in-vitro permettent de modéliser les structures et les fonctions observées dans le cerveau humain. Accéder à l’activité individuelle des neurones sur l’ensemble d’un réseau est un réel défi en neuroscience pour mieux comprendre la complexité des processus qui régissent la communication neuronale. Les techniques actuelles d’enregistrement in vitro (électrophysiologie, imagerie calcique ou encore MicroElectrode ARray) souffrent d’un compromis systématique entre la résolution et la quantité de neurones détectables simultanément (i.e. le champ d’observation).L’objectif de cette thèse est de lever cette contrainte en développant une nouvelle technique d’enregistrement de l’activité neuronale in vitro. L’approche proposée consiste à interfacer les neurones en culture in vitro à un transducteur électro-optique novateur à base de cristaux liquides, capable de convertir les signaux électriques issus de l‘activité neuronale en variation d’intensité optique. Couplé à un capteur imageur adapté (sans lentille de type CMOS, d’une surface de quelques cm² contenant plusieurs millions de pixels, avec une résolution subcellulaire de l’ordre du µm²), ce dispositif devrait permettre l’enregistrement de l’activité neuronale d’un réseau complexe (plusieurs millions de neurones) de manière non invasive (aucun marquage n’est requis), et à la résolution du neurone unique.Une étude théorique couplée à un modèle électrique équivalent a montré que les caractéristiques de détection du dispositif complet (transducteur + capteur optique) étaient en théorie adaptées pour la détection de signaux neuronaux.Un premier prototype a été entièrement élaboré et le procédé de fabrication détaillé. Des caractérisations optiques et électro-optiques ont été menées, validant le fonctionnement même du transducteur et sa fonction d’interrupteur optique variable électriquement contrôlé. Le développement d’une nouvel outil microfluidique chargé d’approfondir les caractérisations et d’évaluer la capacité du dispositif à détecter un champ électrique local équivalent à un signal neuronal a été entamée. La compatibilité du matériau en contact avec les neurones a été évaluée et validéeIn vitro neural networks have proven great potential in neuroscience to provide minimalist yet relevant models to mimic the complexity of human brain circuits. Monitoring the activity of neurons in such systems both at large scale and at single cell resolution represents the main challenge in neuroscience to fully decipher the brain information processing. Current techniques are not suitable to monitor the activity of the entire network (because of the field of view limitations) and at a single cellular resolution.In this work, we introduce a new in vitro neural activity monitoring device. Our approach consists in coupling a neural culture with a liquid crystal based electro optical transducer that will convert the electrical activity of neuronal network in an optical response for each individual neuron. Imaged by a lens-free technique, a CMOS detector that has a large field of view (~cm², up to several millions of pixels with current technologies) and a sub cellular resolution (~µm²), each individual neuron will be monitored by taking a picture of the entire network.The concept study of the transducer and its electrical model show suitable theoretical characteristics of the device for neuronal like signal detection. A first prototype was developed and its fabrication process was entirely detailed. Optical and electro-optical characterization were carried out, revealing the desired electrically controlled light valve effect. The development of a new microfluidic tool was initiated to fully characterize the device and assess its ability to detect local neuronal like spikes. The viability of neuron culture on the transducer material was proved
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Burdakov, Denis. "Regulation of electrical activity of hypothalmic neurons." Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413979.
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Picardo, Michel. "Origine embryonnaire et propriétés morpho-physiologiques des neurones hubs de l'hippocampe en développement." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4057.
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Nous avons récemment mis en évidence des neurones GABAergiques jouant un rôle de « hub » dans l'hippocampe immature, orchestrant la synchronisation neuronale via une arborisation axonale dense. Dans ma thèse, j'ai d'abord montré, grâce à des enregistrements électrophysiologiques par paires, que les hubs étaient connectés à de nombreux neurones par des synapses GABAergiques fonctionnelles (Bonifazi et al. 2009). Puis, en utilisant des souris mutantes conditionnelles où les neurones sont marqués en fonction de leur origine embryonnaire, j'ai démontré que les neurones GABAergiques générés le plus tôt formaient une famille de hubs. Ces neurones sont toujours présents chez l'adulte et deviennent des neurones GABAergiques de projection extrahippocampique. Ceci suggère que la fonction de ces neurones serait maintenue, du moins anatomiquement, au stade adulteWe have recently demonstrated the existence of functional hubs driving network synchronizations in the developing hippocampus. Hubs are a subpopulation of GABAergic neurons displaying widespread axonal projections. During my PhD, using paired electrophysiological recordings, I have shown that hub cells are synaptically connected to a large number of neurons (Bonifazi et al. 2009). Next, using genetic fate mapping approaches, I have demonstrated that early born GABAergic neurons constitute a subpopulation of hub cells. These pioneer hub cells remain into adulthood and develop into GABAergic neurons with an extrahippocampal projection (Picardo et al. 2011). This suggests that hub function may to retained into adulthood, at least structurally
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Wärnberg, Emil. "Modelling Low Dimensional Neural Activity." Thesis, KTH, Beräkningsvetenskap och beräkningsteknik (CST), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-185317.
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A number of recent studies have shown that the dimensionality of the neural activity in the cortex is low. However, what network structures are capable of producing such activity is not theoretically well understood. In this thesis, I discuss a few possible solutions to this problem, and demonstrate that a network with a multidimensional attractor can give rise to such low dimensional activity. The network is created using the Neural Engineering Framework, and exhibits several biologically plausible features, including a log-normal distribution of the synaptic weights.Ett antal nyligen publicerade studier has visat att dimensionaliten för neural aktivitet är låg. Dock är det inte klarlagt vilka nätverksstrukturer som kan uppbringa denna typ av aktivitet. I denna uppsats diskuterar jag möjliga lösningsförslag, och demonstrerar att ett nätverk med en flerdimensionell attraktor ger upphov till lågdimensionell aktivitet. Nätverket skapas med hjälp av the Neural Engineering Framework, och uppvisar ett flertal biologiskt trovärdiga egenskaper. I synnerhet är fördelningen av synapsvikter log-normalt fördelad.
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Siyoucef, Souhila Safia. "Implication des facteurs épigénétiques dans l'épileptogenèse et les déficits cognitifs associés à l'épilepsie du lobe temporal." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM5064.
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L'épilepsie du lobe temporal (ELT) est la forme la plus fréquente de l'épilepsie chez l'adulte. Elle se traduit par des crises spontanées et récurrentes, qui sont résistantes à tout traitement dans 90% des cas. Une agression initiale du cerveau (traumatisme crânien, méningite, convulsions fébriles etc.), est souvent à l'origine de la transformation d'un cerveau « sain » en cerveau épileptique. L'ensemble des processus responsables de cette transition s'appelle l'épileptogenèse. Pouvoir bloquer et/ou retarder l'épileptogenèse chez les patients à risque est une question de santé majeure. En plus des crises, l'ELT soulève d'autres questions. Elle est souvent associée à des déficits cognitifs, qui sont la conséquence de la réorganisation des circuits neuronaux. Ces déficits pourraient être traités de façon indépendante de l'épilepsie elle-même. Le projet de recherche de cette thèse s'inscrit dans ce cadre généralTemporal Lobe Epilepsy (TLE) is the most common form of epilepsy in adults. It translates into spontaneous and recurrent seizures, which are resistant to any treatment in 90% of cases. An initial brain insult (head injury, meningitis, febrile seizures etc.), is often the cause of the transformation of a "healthy" brain into an epileptic one. The process responsible for this transition is called epileptogenesis. Blocking and/or delaying epileptogenesis in at-risk patients is a key issue for public health. In addition to the seizures, TLE raises other problems. It is often associated with cognitive deficits, which are the result of the reorganization of neuronal circuits. These deficits may be treated independently of epilepsy itself. The work presented here fits into this general framework
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Newman, Jonathan P. "Optogenetic feedback control of neural activity." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/52973.
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Optogenetics is a set of technologies that enable optically triggered gain or loss of function in genetically specified populations of cells. Optogenetic methods have revolutionized experimental neuroscience by allowing precise excitation or inhibition of firing in specified neuronal populations embedded within complex, heterogeneous tissue. Although optogenetic tools have greatly improved our ability manipulate neural activity, they do not offer control of neural firing in the face of ongoing changes in network activity, plasticity, or sensory input. In this thesis, I develop a feedback control technology that automatically adjusts optical stimulation in real-time to precisely control network activity levels. I describe hardware and software tools, modes of optogenetic stimulation, and control algorithms required to achieve robust neural control over timescales ranging from seconds to days. I then demonstrate the scientific utility of these technologies in several experimental contexts. First, I investigate the role of connectivity in shaping the network encoding process using continuously-varying optical stimulation. I show that synaptic connectivity linearizes the neuronal response, verifying previous theoretical predictions. Next, I use long-term optogenetic feedback control to show that reductions in excitatory neurotransmission directly trigger homeostatic increases in synaptic strength. This result opposes a large body of literature on the subject and has significant implications for memory formation and maintenance. The technology presented in this thesis greatly enhances the precision with which optical stimulation can control neural activity, and allows causally related variables within neural circuits to be studied independently.
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Ford, Neil C. "Centrifugal Input Modifies Spontaneous Activity of Olfactory Bulb Neurons." Thesis, University of Cincinnati, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1548544.
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The specific aim of this thesis was to examine the effects of centrifugal input on the spontaneous activity of main olfactory bulb (MOB) neurons. Spontaneous activity is the ability of a neuron to generate action potentials in the absence of external stimuli. In order to study the effects of centrifugal fibers on the spontaneous activity of bulbar neurons, impulse conduction of these fibers was blocked using a reversible chemical blockade, while simultaneously recording spontaneous activity in the MOB. Our results show that blocking centrifugal input does modulate the levels of spontaneous activity, indicating that these fibers release neurotransmitters in the steady state. The two pathways by which centrifugal fibers reach the MOB are through the lateral olfactory tract (LOT) and the anterior olfactory nucleus (AON). Lidocaine was applied topically to the LOT or injected into the AON. Electrically evoked field potentials were recorded in the MOB or the AON to demonstrate the efficacy of the lidocaine block and to assess the specificity of the lidocaine application. Single unit activity was recorded from neurons in all layers of the MOB before, during and after lidocaine application.
Topical application of a small cotton ball containing 2% lidocaine significantly reduced the LOT-evoked field potential without affecting the field potentials recorded in the same location in the MOB evoked by olfactory nerve stimulation or AON stimulation. Topical application of lidocaine significantly and reversibly changed the spontaneous activity of neurons in all layers of the MOB. In the mitral cell layer, after the lidocaine blockade of the LOT, some cells decreased their rate of spontaneous activity, and some cells increased their activity. Similar results were obtained in the external plexiform layer, and the granule cell layer. Only a decrease in rate was observed in the glomerular cell layer. Topical application of lidocaine to the LOT had no significant effect on the coefficient of variation of the interspike intervals of spontaneous action potentials and no obvious effect on the entrainment of spontaneous action potentials with respiration.
Preliminary experiments were performed to examine the effects of blocking the AON. Injection of 2% lidocaine into the AON significantly reduced the olfactory nerve and LOT-evoked field potentials recorded in the AON without significantly affecting the field potential recorded in the same location in the MOB. Injection of lidocaine into the AON significantly decreased the spontaneous activity of neurons in the external plexiform layer and the mitral cell layer, no other cell layer was recorded from in these preliminary experiments.
In summary, the data presented in this thesis indicate that centrifugal fibers do indeed release neurotransmitters into the MOB in the steady state. This tonic release modifies the levels of spontaneous activity of bulbar neurons. These results help to elucidate the physiological role of centrifugal input to olfaction.
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Ganguly, Karunesh. "Activity-dependent regulation of neuronal excitability in hippocampal neurons /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2002. http://wwwlib.umi.com/cr/ucsd/fullcit?p3059903.
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Ford, Neil C. "Centrifugal Input Modifies Spontaneous Activity of Olfactory Bulb Neurons." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1368012904.
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Login, Hande. "Activity-regulated retinoic acid signaling in olfactory sensory neurons." Doctoral thesis, Umeå universitet, Institutionen för molekylärbiologi (Medicinska fakulteten), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-89022.
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The aim of the studies included in the thesis is to better understand the interplay between neuronal activity-dependent gene regulation and the bioactive vitamin A metabolite all-trans-retinoic acid (RA) during postnatal development, refinement and maintenance of precise neuronal connectivity using the olfactory sensory neuron (OSN) in the olfactory epithelium (OE) of genetically modified mice as a model. We show that: Inhibition of RA receptor (RAR)-mediated transcription in OSNs reduces expression of the olfactory cyclic nucleotide-gated (CNG) ion channel, which is required for odorant receptor (OR)-mediated stimulus transduction. This, results in increased OSN death and errors in precise connectivity. The increased cell death may be a consequence of reduced intrinsic excitability and/or reduced influx of Ca2+ ions while the errors in connectivity may be due to altered OR-dependent expression of axonal guidance proteins, such as Kirrel-2 and Neuropilin-1. Expression of the RA catabolic enzyme Cyp26B1 in OSNs is positively regulated by RAR-mediated transcription as well as sensory stimulation in a CNG channel-dependent manner. This shows that neuronal activity and local vitamin A metabolism are parts of novel regulatory feedback loop controlling precise connectivity and neuronal survival. The feedback loop may be a form of homeostatic plasticity in response to global changes in neuronal activity. BACE1, an enzyme is implicated in Alzheimer´s disease, and Cyp26B1 are inversely regulated by CNG channel-dependent sensory stimulation. Cyp26B1 expression is switched on at birth, forms a topographic expression gradient in OE and inhibits BACE1 expression into an inverse counter gradient. Taken together these results reveal a novel neuronal activity-dependent mechanism by which sensory stimuli can shape spatial gene expression via altered RA bioavailability. Increased Cyp26B1 expression stimulates turnover of OSNs during adult neurogenesis by a non-cell-autonomous mechanism. The gradient of Cyp26B1 expression correlates with spatially-regulated diversification of OSNs into subpopulations that express different subsets of OR genes. Cyp26B1 expression influences spatial OR diversification of OSNs by two different mechanisms. In the ventrolateral OE, Cyp26B1 inhibits OR expression by blocking OSN differentiation at a stage that may be associated with the cell intrinsic mechanism regulating OR gene choice. In the dorsomedial OE the expression frequency of some ORs is unaltered while other increases, presumably as a consequence of neuronal activity-dependent competition. A probable function of graded and activity-dependent Cyp26B1 expression is to form a topographic partitioning of the olfactory sensory map into functional domains, which gradually differ from each other with regard to experience-driven plasticity and neurogenic potential along the dorsomedial-ventrolateral axis of OE.
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Zhao, Yanmei. "Characteristics of resting membrane potentials and synaptic activity in temperature sensitive and insensitive hypothalamic neurons." Connect to this title online, 2004. http://rave.ohiolink.edu/etdc/view?acc%5num=osu1086184948.
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Thesis (Ph. D.)--Ohio State University, 2004.Title from first page of PDF file. Document formatted into pages; contains xiv, 139 p. : ill. Advisor: Jack A. Boulant, Dept. of Physiology. Includes bibliographical references (p. 127-139).
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Sieling, Fred H. "Prediction and control of patterned activity in small neural networks." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37105.
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Rhythmic neural activity is thought to underlie many high-level functions of the nervous system. Our goals are to understand rhythmic activity starting with small networks, using theoretical and experimental tools. Phase resetting theory describes essential properties that cause and destroy rhythms. We validate and extend one branch of this theory, testing it in bursting neurons coupled by excitation and then extending the theory to account for temporal variability found in our experimental data. We show that the theory makes good predictions of rhythmic activity in heterogeneous networks. We also note differences in mathematical structure between inhibition- and excitation-coupling that cause them to behave differently in noisy contexts and may explain why all central pattern generators (CPGs) found in nature are dominated by inhibition. Our extension of the theory gives a method that is useful to compare experimental and model data and shows that noise may either create or destroy a rhythm. Finally, we described the cellular mechanisms in Aplysia that switch the feeding CPG from arrhythmic to rhythmic behavior in response to reward stimuli. Previous studies showed that a Dopamine reward signal is correlated to changes in electrical coupling and excitability in several important neurons in the CPG. Using the dynamic clamp and an in vitro analog of the full behavioral system, we were able to determine that electrical coupling alone controls rhythmicity, while excitability independently controls the rate of activity. These results beg for further study, including new theory to explain them fully.
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Marissal, Thomas. "Une approche développementale de l' hétérogénéité fonctionnelle des neurones pyramidaux de CA3." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4001/document.
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Les neurones pyramidaux de la région CA3 de l'hippocampe présentent une diversité morphologique, physiologique, biochimique, mais aussi fonctionnelle. Une partie des caractéristiques des neurones étant acquise pendant le développement, nous avons formulé l'hypothèse que la diversité morpho-fonctionnelle des neurones pyramidaux serait déterminée aux stades embryonnaires. Pour tester cette hypothèse, nous avons utilisé des souris transgéniques pour lesquelles l'expression d'un marqueur fluorescent (GFP) est conditionnée par la date de neurogenèse des neurones glutamatergiques. Nous avons enregistré l'activité des neurones en imagerie calcique et montré que les neurones pyramidaux nés le plus tôt déchargent pendant la phase d'initiation des activités épileptiformes générées par le blocage pharmacologique de la transmission GABAergique rapide. De plus, nous montrons que ces neurones précoces possèdent des propriétés morpho-physiologiques distinctes. Enfin, nous montrons que la stimulation de neurones pyramidaux nés tôt peut générer des activités épileptiformes à des stades immatures lorsqu'ils sont stimulés en groupe, et à des stades juvéniles lorsqu'ils sont stimulés individuellement. Ainsi nous démontrons qu'il existe un lien entre la date de neurogenèse et les propriétés morpho-fonctionnelles des neurones pyramidaux de CA3There is increasing evidence that CA3 pyramidal cells are biochemically, electrophysiologically, morphologically and functionally diverse. As most of these properties are acquired during development, we hypothesized that the heterogeneity of the morphofunctionnal properties of pyramidal cells could be determined at the early stages of life. To test this hypothesis, we used a transgenic mouse line in which we glutamatergic cells are labelled with GFP according to their birth date. Using calcium imaging, we recorded multineuron activity in hippocampal slices and show that early generated pyramidal neurons fire during the build-up phase of epileptiform activities generated in the absence of fast GABAergic transmission. Moreover, we show that early generated pyramidal neurons display distinct morpho-physiological properties. Finally, we demonstrate that early generated neurons can generate epileptiform activities when stimulated as assemblies at immature stages, and when stimulated individually at juvenile stages. Thus we suggest a link between the date of birth and the morpho-functional properties of CA3 pyramidal neurons
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Putrino, David. "Single unit and correlated neural activity observed in the cat motor cortex during a reaching movement." University of Western Australia. School of Medicine and Pharmacology, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0124.
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[Truncated abstract] The goal of this research was to investigate some of the ways that neurons located in the primary motor cortex (MI) code for skilled movement. The task-related and temporally correlated spike activity that occurred during the performance of a goal-directed reaching and retrieval task invloving multiple motion elements and limbs was evaluated in cats. The contributions made by different neuronal subtypes loctaed in MI (which were identified based upon extracellular spiking features0 to the coding of movement was also investigated. Spike activity was simulateously recorded from microelectrodes that were chronically implanted into the motor cortex of both cerebral hemispheres. Task-related neurons modulated their activity during the reaching and retrieval movements of one forelimb, or the postural reactions of the contralateral forelimb and ipsilateral hindlimb. Spike durations and baseline firing rates of neurons were used to distinguish between putative excitatory (Regular Spiking; RS) and inhibitory (Fast Spiking; FS) neurons in the cortex. Frame by frame video analysis of the task was used to subdivide each task trial into stages (e.g. premovement, reach, withdraw and feed) and relate modulations in neural activity to the individual task stages. Task-related neurons were classified as either narrowly tuned or broadly tuned depending on whether their activity modulated during a single task stage or more than one stage respectively. Recordings were made from 163 task-related neurons, and temporal correlations in the spike activity of simultaneously recorded neurons were identified using shuffle corrected cross-correlograms on 662 different neuronal pairs.... The results of this research suggest that temporally correlated activity may reflect the activation of intracortical and callosal connections between a variety of efferent zones involved in task performance, playing a role in the coordination of muscles and limbs during motor tasks. The differences in the patterns of task-related activity, and in the incidence of significant neuronal interactions that were observed between the RS and FS neuronal populations implies that they make different contributions to the coding of movement in MI.
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Arib, Ouafa. "Étude électrophysiologique des effets du tabac, de sa fumée et de la nicotine sur des neurones dopaminergiques de l’aire tegmentale ventrale in vivo chez le rat, la souris sauvage et la souris β2 KO." Thesis, Paris Est, 2009. http://www.theses.fr/2009PEST0039/document.
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La nicotine est considérée comme étant la « molécule » addictogène de la cigarette et du tabac. Mais différentes études cliniques, utilisant notamment des substituts nicotiniques, débouchent pratiquement toutes sur une même conclusion : efficacité ne dépassant que de peu celle d’un placebo, et très limitée dans le temps, contrastant avec le pouvoir hautement addictif du tabac, qu'il soit chiqué, prisé ou fumé. Dans ce travail de thèse, nous avons essayé de mettre en évidence le rôle que pourraient avoir certains des autres composés présents dans le tabac ou produits par pyrolyse. Nous avons d’abord utilisé des extraits aqueux de fumée et de tabac pour approcher un aspect global de ce que les fumeurs absorbent chaque fois qu’ils fument une cigarette, nous rapprochant ainsi des conditions physiologiques du fumeur. Puis nous avons choisi un certain nombre de substances. La cotinine, métabolite de la nicotine. L’harmane, une ß-carboline, synthétisée au cours de la combustion et dans l’organisme des fumeurs. La norharmane, une ß-carboline, présente en partie dans le tabac et synthétisée dans la fumée par pyrolyse. La technique utilisée tout au long de ce travail est l’enregistrement électrophysiologique. Cette technique s’applique très bien à l’étude in vivo de différents systèmes neuronaux y compris le système dopaminergique. Nous l’avons utilisée chez le rat, la souris WT et la souris Knockout ß2 (ß2KO). Nous nous sommes intéressés à deux aspects de l’activité cellulaire des neurones dopaminergiques de l’aire tegmentale ventrale : la fréquence de décharge (le firing) et les bouffées (bursts). En parallèle, nous avons conduit des expériences de liaison (binding) sur des cultures de cellules exprimant le récepteur nicotinique α4ß2. Nos résultats les plus significatifs ont montré que : Les bursts sont le plus souvent absents après les injections d’extraits de tabac et de fumée. Cela pourrait, entre autres, impliquer qu’il existe dans le tabac et la fumée des composés autres que la nicotine qui bloquent les effets de la nicotine sur les bursts. Les effets des extraits de tabac et de fumée sur le firing et les bursts ne sont plus présents chez les souris ß2 KO, ce qui implique que l’ensemble des composés du tabac agit essentiellement sur les récepteurs nicotiniques porteurs de la chaine ß2, même si des hypothèses alternatives existent. L’harmane a des effets activateurs très puissants sur le firing des neurones dopaminergiques, et ces effets sont bloqués à 80% par la mécamylamine, ce qui démontre qu’un des principaux composés du tabac et de la fumée autre que la nicotine agit par un mécanisme essentiellement nicotinique. Les expériences de binding confirment que les effets du tabac et de la fumée impliquent les récepteurs nicotiniques d’une façon majeure, mais d’une façon qui diffère légèrement de celle de la nicotine.Les résultats que nous avons obtenus montrent que les effets pharmacologiques du tabac ne se résument pas à ceux de la seule nicotine. Ils peuvent constituer un point de départ pour d’autres travaux, notamment pour étudier de plus près les effets des ß-carbolines. Il est nécessaire d’identifier les types de récepteurs sur lesquels elles se fixent, en utilisant des agonistes et antagonistes de récepteurs aux neurotransmetteurs contrôlant l’activité des neurones dopaminergiques. Des expériences sur des souris transgéniques chez lesquelles différents types de sous-unités de récepteurs nicotiniques ont été supprimés doivent également être envisagées, pour déterminer les mécanismes d’action des composants autres que la nicotine contenus dans le tabac et sa fumée sur les neurones dopaminergiquesNicotine is generally considered as the sole tobacco addictive compound. However, nicotine replacement therapy studies almost all end with the same conclusion: the effectiveness of nicotine replacement is very limited on the short-term, and hardly exceeds that of placebo on the long-term. In addition, studies dealing with the effects of denicotinized cigarettes have provided evidence that these cigarettes have an addictive potential. In the present work, we tried to determine the behavioral role of some tobacco or smoke compounds other than nicotine at the neuronal level. We first compared the effects of nicotine with those of whole tobacco and smoke extracts, given that these preparations closer mimic the smoking situation than nicotine alone. We then examined the effects of a number of selected tobacco or smoke compounds. Cotinine, a major nicotine metabolite. Harmane and norharmane, two ß-carbolines synthesized in smoke as well as in the body of smokers. The technique used consists in the in vivo recording of the firing rate and bursts of dopamine neurons in the ventral tegmental area after intravenous injections of compounds in rats and mice. This electrophysiological technique is known to be a useful way to investigate the properties of selected compounds. In the case of mice, we used wild type and ß2 KO mice. We also made a series of in vitro experiments investigating the binding properties of the compounds on cells expressing high densities of α4ß2 nicotinic receptors. The main results of our studies are the following: Bursts are absent most of the times after the injection of the extracts. These results suggest that tobacco and smoke extracts contain compounds that inhibit the burst-promoting effects of nicotine. Increased firing is no longer present in ß2 KO mice treated with tobacco or smoke extracts, indicating that tobacco and smoke components, as a whole, primarily acts on nicotinic receptors that carry the ß2 chain, although alternative hypotheses may exist. Harmane very strongly activates the firing of dopaminergic neurons. Up to 80% of this effect is blocked by mecamylamine, demonstrating that that a major component of tobacco and smoke other than nicotine acts primarily through a nicotinic mechanism. The binding experiments confirm that the effects of tobacco and smoke involve nicotinic receptors in a major way, but in a way that slightly differs from that of nicotine. Our results may constitute a new starting point for further work, especially for a closer look at the effects of ß-carbolines. Attempts to identify the types of receptors involved in these effects are needed, using agonists and antagonists of neurotransmitter receptors that control the activity of dopamine neurons. Experiments on transgenic mice with deletion of different types of subunits of nicotinic receptors should also be made, to determine the different mechanisms of action of tobacco and smoke compounds other than nicotine on dopaminergic neurons
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Masse, Nicolas. "How neural activity underlies visual motion perception." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=32556.
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Over the last several decades, much progress has been made in understanding how neurons in visual cortex encode various stimuli. However, it is still unclear how their neural response underlies visual perception. The aim of this thesis is to build upon our current understanding of how visual motion perception is generated by sensory neural activity. Many interpretations on how sensory neural activity is combined to form perceptual decisions rely upon the often-observed correlation between neural activity and behavior. Due to its importance, it is critical that we understand whether this correlation is an inherent feature in forming perceptual decisions, or whether it is the result of factors outside the brain. We found that microsaccades, which are small, involuntary eye movements, contribute a small but significant amount to this correlation. This result reinforces the view that the correlation is inherent in forming percepts, but its value has been overestimated in several studies. Given that this correlation between neural activity and behavior is genuine, on what timescales can it operate? We found that the correlation between neural activity and behavior can exist on a timescale of about ten milliseconds. Although our results do not say anything about how visual cortex encodes motion in general, it does suggest that the brain is capable of extracting information from neural responses on fast timescales. If neural activity can be correlated with behavior on fast timescales, can electrical microstimulation be used to demonstrate causality on this temporal regime? By comparing the temporal effects of microstimulation on behavior to an equivalent visual stimulus, we fPendant les quelques dernières décades, beaucoup de progrès a été fait dans notre compréhension à savoir comment les neurones, dans les cortices visuelles, encodent différents stimulus. Toutefois, il n'est toujours pas clair comment les réponses neurales forment la base de la perception visuelle. Le but de cette thèse est d'ajouter à notre compréhension concernant comment la perception de mouvement visuel est générée par l'activité neurale sesnsorielle. Plusieurs interprétations, concernant comment l`activité neurale sensorielle est jointe pour former des décisions perceptuelles, comptent sur la corrélation souvent observée entre l'activité neurale et le comportement. À cause de son importance, il est crucial de comprendre si cette corrélation est un trait inhérant dans la formation des décisions perpceptuelles ou si c'est le résultat de facteurs non reliés au cerveau. Nous avons trouvé que les microsaccades, qui sont de petits mouvements involontaires des yeux, font une petite, mais significante, contribution à cette corrélation. Ce résultat renforce l'opinion que la corrélation est inhérente dans la formation des perceptions, mais sa valeur a été surestimée dans plusieurs études. Étant donné que cette corrélation entre l'activité neurale et le comportement est authentique, sur quelle période de temps peut-elle opérer? Nous avons trouvé que la corrélation entre l'activité neurale et le comportement peut exister dans une période de temps d'environ 10 millisecondes. Bien que nos résultats ne disent rien concernant commnet le mouvement visuel est encodé en général, ils suggèrent que le cerveau est capable d'extraire de
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Andersson, Gabriel. "Decoding Neural Signals Associated to Cytokine Activity." Thesis, KTH, Matematik (Inst.), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-291559.
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The Vagus nerve has shown to play an important role regarding inflammatory diseases, regulating the production of proteins that mediate inflammation. Two important such proteins are the pro-inflammatory cytokines, TNF and IL-1β. This thesis makes use of Vagus nerve recordings, where TNF and IL-1β are subsequently injected in mice, with the aim to see if cytokine-specific information can be extracted. To this end, a type of semi-supervised learning approach is applied, where the observed waveform-data are modeled using a conditional probability distribution. The conditioning is done based on an estimate of how often each observed waveform occurs and local maxima of the conditional distribution are interpreted as candidate-waveforms to encode cytokine information. The methodology yields varying, but promising results. The occurrence of several candidate waveforms are found to increase substantially after exposure to cytokine. Difficulties obtaining coherent results are discussed, as well as different approaches for future work.Vagusnerven har visat sig spela en viktig roll beträffande inflammatoriska sjukdomar. Denna nerv reglerar produktionen av inflammatoriska protein, som de inflammationsfrämjande cytokinerna TNF och IL-1β. Detta arbete använder sig av elektroniska mätningar av Vagusnerven i möss som under tiden blir injicerade med de två cytokinerna TNF och IL-1β. Syftet med arbetet är att undersöka om det är möjligt att extrahera information om de specifika cytokinerna från Vagusnervmätningarna. För att uppnå detta designar vi en semi-vägledd lärandemetod som modellerar dem observerade vågformerna med en betingad sannolikhetsfunktion. Betingandet baseras på en uppskattning av hur ofta varje enskild vågform förekommer och lokala maximum av den betingade sannolikhetsfunktionen tolkas som möjliga kandidat-vågformer att innehålla cytokin-information. Metodiken ger varierande, men lovande resultat. Förekomsten av flertalet kandidat-vågformer har en tydlig ökning efter tidpunkten för cytokin-injektion. Vidare så diskuteras svårigheter i att uppnå konsekventa resultat för alla mätningar, samt olika möjligheter för framtida arbete inom området.
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Larsson, Richard. "Boosting Gamma Neural Activity using Binaural Beats." Thesis, Linköpings universitet, Institutionen för datavetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-166074.
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In this paper, binaural beats were used as stimuli to induce Gamma neural activity in the brains of 18 participants with the purpose to see if the effect enhanced memory and/or speech perception. Participants conducted a word-list recall task, followed by a speech-in-noise task under three conditions: before Gamma stimulus, after Gamma stimulus, and after a placebo stimulus. The results showed that the method works to boost Gamma neural activity, but that neither memory nor speech-perception was significantly affected by the stimulus. The conclusion is that binaural beats is unreliable as a method to enhance memory and speech-perception in humans.
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Mowrer, Samantha M. "Regulatory Focus Modulates Reward-Related Neural Activity." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243952078.
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Kobak, Eva-Maria. "Neural representation of movements : insights from neural activity and from behaviour." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/39132.
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It is long known that the motor cortex is involved in the execution of movements. However, how exactly movements are represented in the brain remains largely unknown. In this thesis, I adopt two different approaches to study natural control of movements. In the first approach, neural signals in the motor cortex are analysed and brought in relation to concurrent movements. In the second approach the behaviour of subjects is observed to deduce characteristics of the underlying neural representations. For the analysis of neural signals, I had access to multi-electrode recordings from motor cortex of behaving monkeys. In the phase of local field potentials, a spatiotemporal pattern resembling a propagating wave can be observed. On a single trial basis, I could show that this pattern is present over a very broad frequency range (0.3???90 Hz) throughout which the wavelength stays relatively constant, causing a linear increase in propagation speed with frequency. Two models, a travelling wavepacket and a dipole model, will be discussed as possible sources of the observed pattern. Additionally, I investigated the information content of the phases of LFP signals with regards to movement direction, which could potentially have implications for the application in a brain machine interface. The behaviour of human subjects was studied in a motor-psychophysical experiment in which a reaching movement was performed under a visuomotor rotation. The two parts of the movement, reaching forward to the target and returning to the starting location, were analysed separately and subjects were prevented from learning the rotation directly in the latter. Thereby, I could estimate the influence of proprioception on backward motor control, and could demonstrate that there is learning transfer between forward and backward movements.
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Ho, S. N. S. "Spontaneous activity and sensory integration in cerebellar neurons in vivo." Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1322702/.
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To understand the information flow in neural circuits, it is essential to determine how neurons translate synaptic input into spike output. In the cerebellum, Golgi cells are the only interneurons that inhibit granule cells in the input layer, where mossy fibre (MF) signals converge onto both cell types. Golgi cells also receive inputs from parallel fibres (PFs, granule cell axons) that form synaptic contacts with the molecular layer interneurons and Purkinje cells. This synaptic organisation suggests the Golgi cells may be an important regulatory element in the cerebellar circuit. In this thesis, I used targeted patch-clamp recordings guided by 2-photon microscopy to examine the synaptic input and spike output patterns of Golgi cells in anaesthetised transgenic mice. I found that Golgi cells received bursty and occasionally rhythmic excitatory inputs and sparse inhibitory inputs in vivo. My results also revealed that Golgi cells exhibit low spontaneous firing rates, and their spiking activity can display 1 Hz rhythmicity and synchrony with millisecond precision. Remarkably, Golgi cells usually generated only a single spike time-locked to the stimulus by integrating multiple synaptic inputs during sensory stimulation. These results suggest that Golgi cells encode temporal information in their spikes, and will therefore transfer this message throughout the cerebellar network by controlling granule cell (PF) activity. Purkinje cells, the sole output neurons of the cerebellar cortex, often display large, single "all-or-none" synaptic responses from the strong excitation by climbing-fibre (CF) inputs in vitro. However, the transmission at the CF-Purkinje cell synapse in the intact brain remains poorly understood. Using whole-cell voltage clamp recordings from Purkinje cells in anaesthetised rats, I revealed that the spontaneous CF excitatory postsynaptic currents (CF-EPSCs) can be bursty, indicating that high-frequency olivary axonal signals are transmitted to the cerebellum in vivo.
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Jensen, Victoria N. "V2a neurons pattern respiratory muscle activity in health and disease." University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1583155179498357.
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Lefebvre, Veronique. "Towards inferring evoked neural activity from haemodynamic changes: nonlinear dynamic modelling of the relationship between stimulus and neural activity." Thesis, University of Sheffield, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489671.
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The blood oxygen level dependent (BOLD) signal acquired by functional magnetic resonance imaging (fMRI) is increasingly used to study neural activation, as it offers excellent spatial and temporal resolutions for a non-invasive technique. However the BOLD signal is indirectly linked to the evoked changes in neural activity. Biophysical frameworks have been developed to relate the stimulus sequence to the BOLD signal through changes in neural activity and haemodynamic variables. The present thesis proposes aJnonlinear dynamic model of the relationship between stimulus and neural activity to be incorporated in the aforementioned frameworks, which until now lacked an accurate representation ofneural activity changes. The first part of the thesis introduces the reader to neuroscience and more specifically to the recent investigations underpinning the BOLD signal. A review of existing neural activity models is then provided to demonstrate the need to find the right balance between simplicity and realism to developing a suitable model in the context of fMRI data interpretation. A simple nonlinear dynamic model describing the amplitude of neural -responses to a stimulus pulse train is presented. Although this model satisfactorily fits the 'profiles of neural activity measurements it was limited to predict only the amplitude information which may not be sufficient in characterising the neural activity changes. A second model is thus proposed, capable of capturing the entire time series of local field potential recordings. Although more complex, this second model is based on the architecture of sensory pathways. While its parameters do not represent physical quantities they may have physiological implications. This model IS successfully usedto infer neural activity changes from blood flow measurements. Both models can predict neural responses profile reliably, for regular and random stimulation pulse trains. The second model can however accept more diverse stimuli types and may he easily extended due to its modular structure. Finally, as weIl as ' being a necessary tool in fMRI interpretation, it is postulated that the model may be used in physiological investigations and for the development of further biophysical models.