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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Signal processing through electroencephalography : Independent project in electrical engineering

Sellergren, Albin, Andersson, Tobias, Toft, Jonathan January 2016 (has links)
This report is about a project where electroencephalography (EEG) wasused to control a two player game. The signals from the EEG-electrodeswere amplified, filtered and processed. Then the signals from the playerswere compared and an algorithm decided what would happen in the gamedepending on which signal was largest. The controls and the gaming mechanismworked as intended, however it was not possible to gather a signal fromthe brain with the method used in this project. So ultimately the goal wasnot reached. / electroencephalography, EEG

Modélisation de l'organisation fonctionnelle de la lecture chez le sujet sain : Etude en EEG-HR par reconstruction de sources et modèles causaux dynamiques. Applications aux patients épileptiques / anatomo-functionnal organization of reading process in healthy subjects and application to epileptic patient : Study in EEG with source reconstruction and dynamic causal modelling

Yvert, Gaëtan 18 June 2012 (has links)
L'écriture et donc a fortiori la lecture est une invention trop récente pour que le substrat neuronal sous tendant ce processus cognitif ait évolué pour se spécialiser dans la reconnaissance visuelle des mots. Ainsi les régions fonctionnelles de la lecture repose à la fois sur les aires corticales dédiées au langage et à la reconnaissance visuelle des objets. Cependant, l'identification complète nécessite au delà du décryptage orthographique, le décodage phonologique ainsi que la récupération de la sémantique. De très nombreuses études en neuroimagerie et en particulier l'IRM se sont intéressées à la localisation des différentes aires fonctionnelles sous tendant ces différentes taches cognitives. Cependant la faible résolution temporelle de l'IRM n'a pas permis de mettre en évidence la dynamique d'intégration au sein du réseau fonctionnel de la lecture. Les enregistrements électrophysiologiques, comme l'EEG, permettent la mise en évidence de la dynamique neuronale grâce à son excellente résolution temporelle. Cependant, la localisation des aires corticales ayant générés les courants de scalp est un problème méthodologique très complexe. Depuis une dizaine d'année, de nombreuses avancées majeures ont été effectuées dans la localisation de source en utilisant des méthodologies nouvelles permettant ainsi de mettre en évidence à la fois les régions fonctionnelles impliquées dans le traitement cognitif ainsi que la dynamique temporelle d'intégration au sein du réseau. Par ailleurs, d'une vision localisationniste, les recherches actuelles tendent vers une vision hodotopique où la fonction d'une région dépend plus de ses connections avec les autres régions du réseau que de sa localisation précise. De nouvelles méthodologies comme les modèles causaux dynamiques permettent de mettre en évidence la structure du réseau et de son fonctionnement. L'objectif de cette thèse a été d'utiliser les derniers outils méthodologiques mis au point afin non seulement de mettre en évidence le réseau de la reconnaissance visuelle des mots mais aussi de proposer un modèle théorique de l'intégration fonctionnelle. En particulier, nous avons mis en évidence l'importance des connexions feedback sur le traitement bottom up de la reconnaissance visuelle des mots à l'instar des objets. Par ailleurs, nous avons appliqué ces méthodologies chez le patient épileptique afin de mettre en évidence les réorganisations fonctionnelles induites par la présence d'un foyer au niveau des régions temporales gauche. / Writing and then a fortiori reading is a too recent invention for evolution to develop a specialized neuronal substrate sustaining the visual word form recognition. Thereby functional region underlying reading process rest on cortical area dedicate to language and visual recognition of objects. However, complete identification of a word requires beyond the orthographic decryption, phonological decoding and semantic recovery. Numerous neuroimaging studies and in particular with fMRI have tried to localize the functional regions sustaining these different cognitive processes. Nonetheless, the weak temporal resolution of fMRI do not allowed revealing the dynamic of integration within the reading network. Electrophysiological recording as EEG permit to show the neuronal dynamic thanks to its excellent temporal resolution. However, localization of the cortical area having generate the scalp electrical field is a complex methodological issue. Since a decade, numerous breakthroughs in methodology allow not only to localize functional region but also the temporal dynamic of their interaction. Moreover, from a localisationnist point of view, current research have adopted an hodotopic vision supposing that the function of a region is more depend of its connectivity with the other region of the network than of its precise location. New methodologies as dynamic causal modeling permit to show the network structure and its dynamic integration. The goal of this thesis has been to use latest methodological development to reveal not only the network of the word recognition, but also to propose a functional model of the integration of the visual stimuli within this network. In particular, we have shown the importance of feedback connection on bottom up processing in word recognition as it has been shown for objects recognition. In addition, we have applied those methodologies to epileptic patients to reveal the influence of a left temporal lesion on the functional reorganization of the reading network.

A Comparative Electroencephalographic Study of Sleep

Schaub, Ronald E. 09 1900 (has links)
This thesis is concerned with the variations which occur in the electroencephalograms, eye-movements, and neck-muscle potentials of three species, the pigeon, rat, and chicken during prolonged recording under normal conditions, under conditions in which the animals were fatigued, and after drugs had been administered. While the recordings from the rat showed the two stages of deep sleep typical of animals, no distinctive ’’sleep” patterns were observed in the records from birds except after Nembutal had been given. The results seem to support the idea that birds do not sleep. / Thesis / Master of Arts (MA)

Classification of Burst and Suppression in the Neonatal EEG

Löfhede, Johan January 2007 (has links)
The brain requires a continuous supply of oxygen and even a short period ofreduced oxygen supply risks severe and lifelong consequences for theaffected individual. The delivery is a vulnerable period for a baby who mayexperience for example hypoxia (lack of oxygen) that can damage the brain.Babies who experience problems are placed in an intensive care unit wheretheir vital signs are monitored, but there is no reliable way to monitor thebrain directly. Monitoring the brain would provide valuable informationabout the processes going on in it and could influence the treatment and helpto improve the quality of neonatal care. The scope of this project is todevelop methods that eventually can be put together to form a monitoringsystem for the brain that can function as decision-support for the physician incharge of treating the patient.The specific technical problem that is the topic of this thesis is detection ofburst and suppression in the electroencephalogram (EEG) signal. The thesisstarts with a brief description of the brain, with a focus on where the EEGoriginates, what types of activity can be found in this signal and what theymean. The data that have been available for the project are described,followed by the signal processing methods that have been used for preprocessing,and the feature functions that can be used for extracting certaintypes of characteristics from the data are defined. The next section describesclassification methodology and how it can be used for making decisionsbased on combinations of several features extracted from a signal. Theclassification methods Fisher’s Linear Discriminant, Neural Networks andSupport Vector Machines are described and are finally compared with respectto their ability to discriminate between burst and suppression. An experimentwith different combinations of features in the classification has also beencarried out. The results show similar results for the three methods but it canbe seen that the SVM is the best method with respect to handling multiplefeatures.

The effect of psychotropic medication on sleep and daytime sleepiness in volunteers and depressed patients

Wilson, Susan Jenifer January 1999 (has links)
No description available.

The use of neural networks in the analysis of the anaesthetic electroencephalogram

Holt, Mark Rowan Gorton January 1997 (has links)
No description available.

Detection of epileptic events in electrencephalograms using artificial neural networks

Khan, Yusuf Uzzaman January 1997 (has links)
No description available.

Event-related potentials as a form of neurofeedback using low-cost hardware

Jacoby, James Derek 31 August 2016 (has links)
The studies reported in this dissertation demonstrate that low-cost hardware is capable of detecting neural responses to stimuli in the user’s focus of attention, and that these responses increase in magnitude with training. Neurofeedback is a sub-category of biofeedback that is concerned with using brain signals as the source of training data in a feedback loop. The neurofeedback training procedures in this dissertation focused on the P300 component, a time-locked event-related potential (ERP) that reflects the cognitive processes of attention and context updating. The current work provides preliminary evidence that neurofeedback based on rewarding a P300-like ERP is effective in increasing the magnitude of this response. Three main questions were examined: 1. Is the Emotiv Epoc, as an example of a low-cost consumer EEG, capable of reliably detecting the P300 component? 2. Is there a training effect whereby the P300 response gets stronger with practice? 3. To what extent is the P300 response affected by cognitive factors such as memory load and self-generation of prompts? The studies employed an open source software framework—open source tools provide a transparent, crowd-supported means of conducting research, but are often difficult to initially use and the current dissertation provides a guide within this content domain. The Emotiv Epoc headset was capable of detecting P300-like ERP in a P3 speller task. The P3 speller is a well-studied paradigm in which users spell letters using only their thoughts as input, while the system determines the letter to be spelled by analyzing the strength and timing of the ERP. Although the analyzed ERP behaved functionally like a P300, and the timing was consistent, the spatial localization of the signal was more frontally dominant than a standard P300. In the training study, 12 participants completed five P3 spelling sessions. Although an ERP training effect was observed, participant motivation and fatigue modulated this effect. In an attempt to improve motivation and increase interest in the task, a novel card game task was introduced. In this task—a variant of the card game “Concentration,” where players turn cards face-up one at a time to match pairs—the participants used an attentional mechanism to select cards. This allowed for attentional training while offering a task whereby cognitive difficulty could be manipulated. In these studies, the P300-like ERP proved itself to be robust in regards to changes in cognitive difficulty, as well as internal versus external generation of prompts. This led to confidence in the separation of underlying cognitive and attentional processes and validated the focus of the P300 ERP on the attentional process. The results indicated that ERP-specific neurofeedback is effective in increasing ERP magnitude. This dissertation does not involve any clinical populations as study participants, but the long-term potential of this research is to directly train a brain response relevant to clinical conditions. The paradigm can be implemented using low-cost hardware as opposed to research-grade instruments, which increases the likelihood of further research by the clinical community and lowers the barrier of entry for future exploration of the techniques. / Graduate / 0633 / derekja@uvic.ca

Dynamics Of Cognitive Control And Midline Theta Activity Across Multiple Timescales

January 2016 (has links)
Humans frequently encounter cognitive conflict situations, such as the need to ignore distractions or make a decision with multiple options. Cognitive control over attention and behavior in conflict situations is a basic executive functioning skill vital for goal-oriented behaviors. Musicians spend many hours exercising cognitive control while ignoring distractions, focusing on specific sounds, and avoiding incorrect movements. Therefore, musicians are a useful population to examine the effects of long-term experience on cognitive control. The current study used independent component analysis, time-frequency analysis, and ERP analysis on electrophysiological data to identify neocortical activity and timescales of cognitive control during an auditory Simon Task. Musicians showed no cognitive control advantage over non-musicians. Consistent with previous research, we found short-term compatibility sequence effects as well as longer-term effects of base rate (proportion of compatible trials) in response time Simon effect data. Sequence effects and a base rate x compatibility interaction also emerged for some ERP and ERSP components, including frontal theta in the ERSPs. We then used predictive models to test whether changes in the Simon effect across base rates were due to changing numbers of each sequence type that necessarily accompany base rate manipulations. Results indicate that sequence effects account for 17% of the reaction time cognitive control shift associated with proportion compatible manipulations. The base rate manipulation affected behavior and neural correlates above and beyond sequence effects. / Lisa Chinn

Electrode performance and signal processing strategies for the discrimination of EEG alpha waves: implications for environmental control by unconstrained subjects without training.

Searle, Andrew. January 2000 (has links)
The phenomenon of the increase in alpha EEG activity associated with eye closure has been shown to be successful for implementing environmental control for disabled persons. Studies in this thesis investigate strategies which improve the reliability, robustness, and ease of use of alpha EEG control systems. Primarily, research covers the effectiveness of alpha EEG detection algorithms (with regard to detection time and susceptibility to artifact) and the construction and use of EEG sensing electrodes. Many new techniques for the detection of the increase of alpha EEG associated with eye closure are researched, developed, implemented and evaluated. All detection techniques are compared to a conventional method using a novel performance parameterisation criterion. In conjunction with the application of the same EEG data sets to all techniques, the use of the performance criteria enables a fair and quantitative comparison to be made between alpha detection methodologies. Detection techniques employed include enhanced versions of conventional methods, localisation of apparent alpha sources in the brain, and preprocessing methods (such as spatial filtering, adaptive filtering and independent component analysis). The best performance of alpha EEG detection was given by the source power alpha localisation technique, which showed statistically significant and practically important improvements in performance over conventional techniques. Additionally, this localisation technique is convenient and fast to implement. In situations in which electrodes are intended for unsupervised use with environmental control systems, the evaluation of alternative electrode types to the conventional wet electrodes is required, as the use of wet electrodes has several drawbacks. The performance of wet, dry and insulating electrodes is compared in this research. One aspect of the quantitative comparison of electrodes types is the measurement of contact impedance. To enable the fast and accurate measurement of impedance spectra, a new impedance spectroscopy system was developed as part of this thesis. In addition to comparison of impedance criteria, electrodes were evaluated in the presence movement-based, and electric field induced, artifacts. The electrode comparisons were carried out in a direct and quantitative manner in a controlled test environment for the first time. Results indicate that, in contrast to earlier reports, both dry and insulating electrode perform well with respect to artifact and offer a viable alternative to wet electrodes for long-term monitoring of biosignals from the surface of the skin. More improvements are required before such electrodes are suitable for EEG usage.

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