Tesis sobre el tema "FMRI"
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Turkay, Kemal Dogus. "Simulated Fmri Toolbox". Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12611465/index.pdf.
Texto completoAllan, Thomas. "Novel fMRI analysis". Thesis, University of Nottingham, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.659287.
Texto completoPavlicova, Martina. "Thresholding FMRI images". The Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1097769474.
Texto completoPavlicová, Martina. "Thresholding FMRI images". Connect to this title online, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1097769474.
Texto completoTitle from first page of PDF file. Document formatted into pages; contains xvii, 109 p.; also includes graphics (some col.) Includes bibliographical references (p. 107-109). Available online via OhioLINK's ETD Center
Barreto, Felipe Rodrigues. "O acoplamento neurovascular e metabólico do córtex visual ativado de sujeitos jovens saudáveis durante a disponibilidade reduzida de oxigênio". Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/59/59135/tde-29092016-142720/.
Texto completoThe cerebral tissue is highly dependent on a complex vascular network and a tight regulated supply of oxygen, since oxidative metabolism is the primary source of ATP synthesis. Increased neuronal activity leads to a well-established mismatch between CBF and CMRO2, measured by PET and nuclear magnetic resonance techniques. The much larger CBF evoked response as compared to CMRO2 response raises questions about the role played by oxygen as a potential limiting factor. Despite the devastating effects of intense hypoxia to cerebral tissue, moderate oxygen deprivation through short periods of time is frequent in chronic disorders such as obstructive sleep apnea and has been suggested to be a risk factor for morbidities such as hypertension and stroke. Identifying the impact of mild hypoxia on functional brain metabolism in the healthy human brain is a crucial step for understanding basics aspects of cerebral bioenergetics and its relationship with the neurovascular system. In this thesis we evaluate the impact of reduced oxygen availability in the neurovascular and metabolic coupling of the healthy human brain. Two studies were performed in the presence of mild hypoxia, with 80 to 85% arterial blood oxygen saturation, and normoxia as the control condition. The first study utilized functional Magnetic Resonance Imaging techniques (fMRI) at 3T to characterize the vascular response to visual stimulation in 9 subjects. The second study aimed at characterizing the neurochemical profile of the human brain and quantifying the stimulus-induced metabolic changes as measured by fMRS at 7T in 11 subjects. The fMRI data showed significant reductions in the recruited cortical areas during mild hypoxia, although activated areas in all three imaging modalities showed responses with similar amplitude of blood flow and volume from normoxia. In addition, the variation of oxygen consumption due to stimulation was smaller during mild hypoxia. These findings could potentially suggest decreased neuronal recruitment, although a new decoupling between neuronal activity and vascular response (i.e. similar neuronal recruitment with different vascular response) could not be discarded. The fMRS study showed similar stimulus-induced glutamate and lactate changes during both gas conditions. However, significant concentration differences were observed in aspartate, glutamate and glutamine during rest conditions. Finally, the combination of the data from the two studies herein presented suggests that mild hypoxia does not result in reduced neuronal recruitment despite the altered vascular response, as shown by the similar glutamate and lactate stimulus-induced responses, known to be strong markers of increased neuronal activity. However, there are evidences that support altered neurovascular coupling and metabolic concentrations during reduced oxygen availability at rest. Further analysis will be necessary to elucidate how the new steady state concentrations of aspartate, glutamate and glutamine could be linked to physiological mechanism that potentially alters the neurovascular response.
Bungert, Andreas. "TMS combined with fMRI". Thesis, University of Nottingham, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.546548.
Texto completoBischoff, Matthias [Verfasser]. "Neurofunctional correlates of audiovisual binding in fMRI, EEG and EEG-guided fMRI / Matthias Bischoff". Gießen : Universitätsbibliothek, 2014. http://d-nb.info/1068589051/34.
Texto completoSoldati, Nicola. "Novel data-driven analysis methods for real-time fMRI and simultaneous EEG-fMRI neuroimaging". Doctoral thesis, University of Trento, 2012. http://eprints-phd.biblio.unitn.it/842/1/Soldati_PhD_thesis.pdf.
Texto completoDrobnjak, Ivana. "FMRI simulator : development and applications". Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.444904.
Texto completoDe, Luca Marilena. "Low frequency signals in FMRI". Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.418562.
Texto completoZwaag, Wietske van der. "Techniques for high-performance fMRI". Thesis, University of Nottingham, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436813.
Texto completoOu, Wanmei. "fMRI detection with spatial regularization". Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33856.
Texto completoIncludes bibliographical references (p. 99-102).
Functional Magnetic Resonant Imaging (fMRI) is a non-invasive imaging technique used to study the brain. Neuroscientists have developed various algorithms to determine which voxels of the images are active. Most of these algorithms, operating on the signal of each voxel separately, are referred to as the voxel-by-voxel detectors. Among those voxel-by-voxel detectors, paired T-test and General Linear Model (GLM) are the most popular. The Mutual Information (MI) based detector has recently been introduced. It is interesting to compare these three detectors' modeling assumptions, as well as their performance, in order to understand their advantages and shortcomings. Due to the low signal-to-noise ratio (SNR), the voxel-by-voxel detectors usually result in fragmented activation pattern, which is not in agreement with our understanding of brain activation. The biological models of brain activation suggest that adjacent locations of the brain tend to be in the same activation state. We take advantage of these models and apply a Markov Random Field (MRF) spatial prior to the statistics provided by the voxel-by-voxel algorithms. MRF has been shown to be able to overcome the effect of over-smoothing, which is the major drawback of the conventional spatial regularization models such as the Gaussian smoothing model.
(cont.) We adopt Mean Field, a variational algorithm, to estimate the MRF solution. We show that Mean Field can provide reasonable approximation compared with the exact solver in the case of binary MRFs, while reducing the computations by one to two orders of magnitude in our simulated and real data sets. In addition, unlike the exact solver, it can handle multiple-state MRFs. Inspired by atlas-based segmentation, we further refine the spatial regularization process by incorporating anatomical information, such as segmentation results from Magnetic Resonance Imaging (MRI), into the MRF prior. The extended MRF model encodes both tissue type and activation state. To our knowledge, our approach is the first spatial smoothing method that utilizes anatomical information without cortical surface extraction. To evaluate the smoothing models, we performed ROC and confusion matrix analysis on synthetic data. We also evaluate them by studying their ability to recover activation from significantly shorter time course using real data. Including anatomical information improves detection accuracy for both the Gaussian-smoothing-based detector and the MRF-based detector. The Gaussian-smoothing model provides poor results if we are interested in both positive and negative activation regions in the brain.
(cont.) Furthermore, the anatomically guided MRF-based detector improves the detection quality compared with the anatomically guided Gaussian-smoothing-based detector for standard fMRI in standard SNR quality.
by Wanmei Ou.
S.M.
Tijssen, Hendrikus N. "Novel methods for brainstem FMRI". Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:ed8e4c4f-5152-44e4-936f-ccf6092d904b.
Texto completoManczak, Tiago. "Estimulador galvânico vestibular para fMRI". Universidade Tecnológica Federal do Paraná, 2012. http://repositorio.utfpr.edu.br/jspui/handle/1/406.
Texto completoThis work presents the development of a galvanic vestibular stimulator to be used in functional magnetic resonance imaging experiments (fMRI). In fMRI experiments it is required the production of somatosensory stimuli in the patient must be sincronized with the fMRI pulse sequence. The stimulator circuits were divided in analog circuits (placed within the magnet room) and digital circuits (placed in the MRI command room). The communication between the circuits is made through optical fiber. fMRI experiments performed with volunteers demonstrated that the proposed stimulator is able to keep the sincronization with the MRI system and can be used to locate the brain areas that are activated by the vestibular system.
Nováková, Marie. "Mapování pohybových artefaktů ve fMRI". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-220039.
Texto completoRocchi, Federico. "Chemogenetic modulation of fMRI connectivity". Doctoral thesis, Università degli studi di Trento, 2022. http://hdl.handle.net/11572/335219.
Texto completoYildirim, Funda. "Localization Facial Symmetry Perception Through Fmri". Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12615040/index.pdf.
Texto completoBai, Ping Truong Young K. Smith Richard L. "Temporal-spatial modeling for fMRI data". Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2007. http://dc.lib.unc.edu/u?/etd,1481.
Texto completoTitle from electronic title page (viewed Apr. 25, 2008). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Statistics and Operations Research." Discipline: Statistics and Operations Research; Department/School: Statistics and Operations Research.
Woolrich, Mark. "Model-based approaches to FMRI analysis". Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249485.
Texto completoPlumpton, Catrin Oliver. "Classifier ensembles for streaming fMRI data". Thesis, Bangor University, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540419.
Texto completoRollings, David T. "EEG-fMRI in epilepsy and sleep". Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7287/.
Texto completoRülander, Britta Angela. "Galvanic vestibular stimulator for fMRI research". Universidade Tecnológica Federal do Paraná, 2016. http://repositorio.utfpr.edu.br/jspui/handle/1/1843.
Texto completoThis master thesis presents the further development of a galvanic vestibular stimulator for use in fMRI examinations developed in a previous thesis (MANCZAK, 2012). This thesis amends the GVS by circuits to measure feedback values and implements the stimulation circuit with digital components, such as a microcontroller and flyback integrated circuits. The microcontroller is used in order to control the current source and process the measured values. The communication between the PC, which allows user interaction through a graphical user interface, and the microcontroller is implemented through optical communication, which is defined by a communication protocol specification. The digital circuitry is designed to be placed within the MRI room, meeting the requirements imposed by strong magnetic fields and radio frequency pulses. The underlying hypothesis of the thesis is that the device can be placed within the MRI room without having a negative impact on the MRI image quality. Laboratory tests without the MRI confirmed the correct design of the galvanic vestibular stimulator.
Zeledon, Lostalo Emilia Maria. "FMRI IMAGE REGISTRATION USING DEEP LEARNING". OpenSIUC, 2019. https://opensiuc.lib.siu.edu/theses/2641.
Texto completoMcEvoy, Bradley Wright. "Spatial Bayesian variable selection and fMRI". Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=1709046681&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
Texto completoPerez, Carlos Arturo. "Discovering causal relationships from fMRI data". [Pensacola, Fla.] : University of West Florida, 2009. http://purl.fcla.edu/fcla/etd/WFE0000189.
Texto completoSubmitted to the Dept. of Computer Science. Title from title page of source document. Document formatted into pages; contains 90 pages. Includes bibliographical references.
Bartoň, Marek. "Dekonvoluce hemodynamické odezvy z dat fMRI". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2011. http://www.nusl.cz/ntk/nusl-219259.
Texto completoGathers, Ann D. "DEVELOPMENTAL FMRI STUDY: FACE AND OBJECT RECOGNITION". Lexington, Ky. : [University of Kentucky Libraries], 2005. http://lib.uky.edu/ETD/ukyanne2005d00276/etd.pdf.
Texto completoTitle from document title page (viewed on November 4, 2005). Document formatted into pages; contains xi, 152 p. : ill. Includes abstract and vita. Includes bibliographical references (p. 134-148).
Tuan, August Saul. "fMRI representation of transient onsets and adaptation". Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2006. http://wwwlib.umi.com/cr/ucsd/fullcit?p3214711.
Texto completoTitle from first page of PDF file (viewed June 30, 2006). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 86-92).
Keinänen, T. (Tuija). "Infra-slow fluctuations in simultaneous EEG-fMRI". Doctoral thesis, Oulun yliopisto, 2016. http://urn.fi/urn:isbn:9789526213880.
Texto completoTiivistelmä Aivojen toiminta vaihtelee monissa avaruudellisissa ja ajallisissa mittakaavoissa. Toiminnallisissa magneettikuvauksissa (TMK) on havaittu, että veren happipitoisuudesta riippuvan (engl. BOLD) signaalin erittäin hitaat vaihtelut ovat järjestäytyneet hyvin määriteltyihin alueisiin, joita kutsutaan lepotilahermoverkostoiksi. Erittäin hitaita vaihteluita on havaittu myös täysikaistaisesta aivosähkökäyrästä (fbEEG). Viime vuosina nämä kaksi menetelmää on usein yhdistetty tarkemman mittaustuloksen aikaansaamiseksi. Samanaikaisissa EEG-TMK-mittauksissa BOLD signaalin erittäin hitaiden vaihteluiden on huomattu korreloivan nopeampien elektrofysiologisten värähtelyjen amplitudien verhokäyrien kanssa, mikä viittaa samaan perustana olevaan neuraaliseen dynamiikkaan. Myös suoria korrelaatioita on löydetty tehtäviin liittyvissä tutkimuksissa, mutta ei aiemmin lepotilatutkimuksissa. Lepotilan EEG:n ja BOLD-signaalin suhteen ymmärrys voi osoittautua hyödylliseksi aivojen perustilan aktiivisuuden vaihteluiden tutkimisessa. Hermoverkostojen toiminnallisen liittyvyyden on todettu huojuvan tietyissä tehtävissä ja joissain sairauksissa, mutta myös lepotilassa terveillä henkilöillä. Runsaasta tutkimuksesta huolimatta ei liittyvyyden huojunnalle ole vielä löytynyt selkeää aiheuttajaa. Näiden avoimien kysymysten tutkimiseksi suoritimme yhdenaikaisia fbEEG-TMK-mittauksia. Kummankin modaliteetin mittaustuloksia analysoitiin itsenäisten komponenttien analyysillä tulosten vertailtavuuden parantamiseksi. Korrelaatioanalyysit osoittivat, että EEG:n erittäin hitaat vaihtelut korreloivat ajallisesti ja avaruudellisesti TMK:n BOLD-signaalin kanssa. Näissä korrelaatioissa esiintyi sekä paikkaan että aikaan liittyvää huojuntaa, joka oli yhteydessä lepotilahermoverkostojen toiminnallisen liittyvyyden vahvuuteen. Nämä tulokset viittaavat siihen, että samat tekijät tuottavat EEG:n ja TMK:n BOLD-signaalien hitaat vaihtelut. EEG:n ja TMK:n signaalien erittäin hitaiden vaihteluiden välisen korrelaation ymmärtäminen antaa perustason tietoa aivojen toiminnan dynamiikasta sekä siihen vaikuttavista tekijöistä. Parempi ymmärrys aivotoiminnan taustoista auttaa kehittämään tehokkaampia hoitoja neurologisiin sairauksiin, kun tieto mekanismeista niiden takana tarkentuu. Mahdollisuus mitata lepotilahermoverkostojen toimintaa EEG:llä aiempaa tarkemmin voi auttaa kehittämään uusia menetelmiä sairauksien varhaiseen diagnostiikkaan
Liu, Aiping. "Brain connectivity network modeling using fMRI signals". Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/58126.
Texto completoApplied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
Hollinger, Avrum. "Design of fMRI-compatible electronic musical interfaces". Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=116045.
Texto completoMullinger, Karen Julia. "Simultaneous EEG and fMRI at high fields". Thesis, University of Nottingham, 2008. http://eprints.nottingham.ac.uk/14142/.
Texto completoHe, Jiabao. "Functional brain imaging with fMRI and MEG". Thesis, University of Nottingham, 2005. http://eprints.nottingham.ac.uk/12371/.
Texto completoBalcı, Serdar Kemal. "Classification of whole brain fMRI activation patterns". Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45854.
Texto completoIncludes bibliographical references (p. 59-62).
Functional magnetic resonance imaging (fMRI) is an imaging technology which is primarily used to perform brain activation studies by measuring neural activity in the brain. It is an interesting question whether patterns of activity in the brain as measured by fMRI can be used to predict the cognitive state of a subject. Researchers successfully employed a discriminative approach by training classifiers on fMRI data to predict the mental state of a subject from distributed activation patterns in the brain. In this thesis, we investigate the utility of feature selection methods in improving the prediction accuracy of classifiers trained on functional neuroimaging data. We explore the use of classification methods in the context of an event related functional neuroimaging experiment where participants viewed images of scenes and predicted whether they would remember each scene in a post-scan recognition-memory test. We view the application of our tool to this memory encoding task as a step toward the development of tools that will enhance human learning. We train support vector machines on functional data to predict participants' performance in the recognition test and compare the classifier's performance with participants' subjective predictions. We show that the classifier achieves better than random predictions and the average accuracy is close to that of the subject's own prediction. Our classification method consists of feature extraction, feature selection and classification parts.
(cont.) We employ a feature extraction method based on the general linear model. We use the t-test and an SVM-based feature ranking method for feature selection. We train a weighted linear support vector machine, which imposes different penalties for misclassification of samples in different groups. We validate our tool on a simple motor task where we demonstrate an average prediction accuracy of over 90%. We show that feature selection significantly improves the classification accuracy compared to training the classifier on all features. In addition, the comparison of the results between the motor and the memory encoding task indicates that the classifier performance depends significantly on the complexity of the mental process of interest.
by Serdar Kemal Balcı.
S.M.
Sander, Christin Y. (Christin Yen-Ming). "Simultaneous PET/fMRI for imaging neuroreceptor dynamics". Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/93832.
Texto completoCataloged from PDF version of thesis.
Includes bibliographical references (pages 147-158).
Whole-brain neuroimaging is a key technique for studying brain function and connectivity. Recent advances in combining two imaging modalities - magnetic resonance imaging (MRI) and positron emission tomography (PET) - into one integrated scanner, have created the opportunity to explore the underlying neurochemistry of brain function in more detail. Imaging these dynamics plays an important role for understanding drug action and function of neurochemical pathways in the brain and is crucial, yet largely unexplored, for creating and evaluating treatment of neurological and psychiatric disorders. In this thesis, we first address technological challenges in simultaneous PET/MRI by designing, building and evaluating PET compatible MR probes for brain imaging, which enable highly sensitive dual modality imaging. We then develop simultaneous imaging methods with PET and functional MRI to assess and validate relationships between receptor occupancy and changes in brain activity due to pharmacological challenges targeting the dopamine system. Our results indicate that dopamine receptor occupancies and vascular responses are correlated in anatomical space and with pharmacological dose. Moreover, the temporal dynamics of the signals show that a direct neurovascular coupling between receptor occupancy and hemodynamics exists and that a temporal divergence between PET and fMRI can be used to investigate previously unexplored neurochemical parameters and adaptation mechanisms in vivo. Overall, our findings provide insight into dopaminergic receptor dynamics and their effects on high-level brain function, paving a way to address receptor-specific brain dysfunction effectively.
by Christin Y. Sander.
Ph. D.
Tobón, Gabriel Andres. "Spatial alignment of functional regions in fMRI". Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/66810.
Texto completoCataloged from PDF version of thesis.
Includes bibliographical references (p. 49-50).
An essential step for discovering a common structure in brain activation regions from multi-subject fMRI data is the ability to find spatial correspondences across subjects. This has proven to be a challenging problem due to the lack of a ground truth and variability in anatomical brain structure, functional activation, and spatial locations of functional regions. Standard methods rely on the correspondences given by anatomical registration to a common space, but fail to account for spatial variability of the functional regions relative to anatomy. We develop a clustering method that relies on the alignment of both the anatomical structure and the functional landmarks. The method is shown to improve over standard group analysis techniques that rely on anatomical alignment only. The validation of our method confirms that peaks of activation exhibit consistent spatial structure. Furthermore, our work creates a framework for future testing of different metrics for similarity of brain activation regions across subjects.
by Gabriel Andres Tobón.
M.Eng.
Habes, Isabelle. "Real-time fMRI-based neurofeedback in depression". Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/59751/.
Texto completoTalasu, Dharneesh. "Efficient fMRI Analysis and Clustering on GPUs". The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1322077186.
Texto completoMcGregor, Keith Matthew. "Negative BOLD and aging an fMRI study /". [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0013860.
Texto completoOrff, Henry John. "Neurobiology of insomnia as measured with FMRI". Diss., [La Jolla] : [San Diego] : University of California, San Diego ; San Diego State University, 2010. http://wwwlib.umi.com/cr/ucsd/fullcit?p3389700.
Texto completoTitle from first page of PDF file (viewed February 17, 2010). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 81-86).
Štens, Radovan. "Analýza obrazových dat funkční magnetické rezonance (fMRI)". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2010. http://www.nusl.cz/ntk/nusl-375489.
Texto completoLee, Woogul. "Neural substrates of intrinsic motivation: fMRI studies". Diss., University of Iowa, 2011. https://ir.uiowa.edu/etd/2738.
Texto completoAndrade, Katia Cristine. "Dinâmica da alteração perfusional induzida por estado de apnéia utilizando fMRI". Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/59/59135/tde-20042010-100103/.
Texto completoThe BOLD (Blood Oxygenation Level Dependent) signal, is the most used contrast mechanism of the so called functional Magnetic Resonance Imaging (fMRI). Although it indirectly measures neuronal activity, its response is directly related to cerebral blood flow (CBF), Cerebral Metabolic Rate of Oxygen (CMRO2) and Cerebral Blood Volume (CBV) and can be, in principle, used to map cerebral perfusion. Thus, the main purpose of this study was to investigate, quantitatively, some aspects of perfusional alterations in the human brain. These changes were mapped by changes in the BOLD signal as a result of a global and uniform stimulation: hypercapnia induced by breath holding paradigms. Magnetic resonance images were acquired in a 1.5 T scanner (Siemens, Magneton Vision) with EPI-BOLD fMRI sequences. It was analyzed the BOLD dependency on breath holding duration and differences on the BOLD signal due the employed breath holding techniques: breath holding after expiration or after inspiration. The regional variability of the BOLD signal propagation was also studied. Moreover, the signal was used to construct maps based on CBV information. It was possible to gain information about the BOLD signal behavior that respond to PaO2 and PaCO2 alterations. Besides, it was demonstrated its regional variations sensibility, which can be correlated with arterial reactivity or the rest CBV of this arteries. It was also possible acquire information about the temporal characteristics of CBF changes induced by hypercapnia across brain regions as well as the identification of cortical areas that were responsible to the voluntary breathing. Finally, the B-CBV maps that used the BOLD con-trast were able to reflect CBV information, although, it is necessary the study of other parameters that can influence the signal.
Peres, André Salles Cunha. "Implementação de um sistema de localização espacial de regiões cerebrais em tempo real para aplicação de TMS por co-registro com fMRI". Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/59/59135/tde-21052009-151939/.
Texto completoIn the last 20 years we witnessed a great advance in neurosciences and evaluation techniques as an initial attempt for understanding of working principles of the human central nervous system Techniques such as electroencephalography (EEG), positron emission tomography (EEG), functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) have produced grate advances in the understanding of human cerebral nervous system. fMRI generates statistical maps of the cerebral activity and TMS uses intense and fast magnetic pulses to produce a high rate magnetic flux variation to produce cortical electrical stimulation. However, even today TMS uses subjective parameters to establish an area responsible for a certain stimulated activity, that does not allow the precise cortical localization of the cortex area being stimulated by the magnetic pulse. Aiming to overcome this subjectiveness to more precisely stimulate the activity center this work investigates the use of a co-register method based on TMS and fMRI through the use of a neuronavigator that allows the location of brain structures below a certain scalp position. Initially the TMS was characterized and a map of the magnetic field intensity produced by the eight shaped or butterfly coils was determined by different methods. After this step a neuronavigator was devel-oped allowing a superposition of the magnetic field pattern with the fMRI images. The coil position can be varied and the possible stimulated regions can be visualized. This integration of information is expected to improve the TMS accuracy. To verify the efficacy of this method the motor cortex of 10 asymptomatic volunteers were stimulated. The stimulus was monitored with an electromyogram acquired in the hand thumb abductor muscle. The results shown that with the neuronavigation it was possible to stimulate the desired motor region in all the volunteers studied.
Pastorello, Bruno Fraccini. "Em busca da região epileptiforme em pacientes com epilepsia do lobo temporal: métodos alternativos baseados em fMRI e EEG-fMRI". Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/59/59135/tde-26102011-135335/.
Texto completoTemporal lobe epilepsy (TLE) is the most common and resistant form of epilepsy to anti-epileptic drug. There are several types of anti-epileptic drugs used in seizure control. However, in some cases drug treatment is not effective and surgery to remove the epileptogenic zone (EZ) is a recommended alternative. EZ is a theoretical concept and there are many techniques that have been applied to enclose it precisely. In practice, EEG, video-EEG, MEG, SPECT, PET and various MRI techniques, especially functional MRI (fMRI), have been used to map areas related to EZ. However, in some cases, the results remain non-convergent and the EZ, undefined. Therefore, the use of new methodologies to assist the location of EZ have been proposed. Herein, our goal was to develop two methods for assessing the EZ. The first one was designed to access changes in the hemodynamic response (HRF) of the EZ in response to hypercapnia. 22 patients with TLE and 10 normal volunteers were evaluated by modulating the partial pressure of CO2 during the acquisition of fMRI in a breathing holding and a passive inhalation CO2/air protocols. The results show increased onset times and decreased amplitude of the HRF in the temporal lobe of TLE patients compared with asymptomatic volunteers. Moreover, most patients had onset maps coincident with ictal SPECT localizations. The second proposed study was based on simultaneous EEG-fMRI acquisitions. The relationship between powers of alpha and theta bands (EEG) and BOLD contrast (fMRI) was investigated in 41 TLE patients and 7 healthy controls. Alpha band results show a consistent negative correlation in the occipital, parietal and frontal lobes both in controls and TLE patients. In addition, controls show disperse positive correlations in both hemispheres. On the other hand, TLE patients presented strong positive correlations in the thalamus and insula. Theta band analysis, in controls, primarily show positive correlations in bilateral pre-and post-central gyri. In patients, robust positive correlations were observed in the anterior cingulate gyrus, thalamus, insula, putamen, superior parietal, frontal and temporal gyri. Moreover, the lateralization index (LI) indicates a coincidence between the side of the EZ evaluated by clinical diagnosis and clusters detected in the theta band. In conclusion, the hipercapnia study showed to be an interesting tool in locating EZ and the results are similar to SPECT findings. The longer onset and lower amplitude of the HRF observed in patients may be related to a vascular stress due to the recurrence of seizures. Furthermore, alpha and theta rhythms may be a promising tool to be used in determining the lateralization of EZ in patients with TLE.
Conner, Ian Patrick. "fMRI studies of amblyopia pediatric and adult perspectives /". Morgantown, W. Va. : [West Virginia University Libraries], 2005. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4077.
Texto completoTitle from document title page. Document formatted into pages; contains xi, 199 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.
Leung, Tsan-chiu. "An fMRI study of conceptual combination in Chinese". Click to view the E-thesis via HKUTO, 2004. http://sunzi.lib.hku.hk/hkuto/record/B3105870X.
Texto completoGlomb, Katharina. "Spatio-temporal dynamics of human fMRI resting rate". Doctoral thesis, Universitat Pompeu Fabra, 2017. http://hdl.handle.net/10803/402438.
Texto completoLa actividad cerebral espontánea, o actividad de reposo, es aquella que uno puede registrar cuando el cerebro no está involucrado en ninguna tarea impuesta del exterior (tal como sería la presentación de un estímulo). El estudio de la actividad de reposo ha conocido un interés creciente durante los últimos 20 años. Si bien las fluctuaciones en la actividad de reposo eran conocidas desde los inicios de la electrofisiología moderna, el descubrimiento, en 1995, de que estas fluctuaciones muestran patrones espaciotemporales robustos ha tenido un impacto profundo en la manera de entender e investigar la actividad del cerebro. En esta disertación caracterizamos la dinámica espaciotemporal de la actividad de reposo a nivel macroscópico usando registros de fMRI en humanos y combinando nuevas herramientas de análisis y modelos teóricos del cerebro a gran escala. Observamos patrones comunes de conectividad funcional evolviendo en el tiempo tanto en los datos empíricos como en las simulaciones. Demostramos que las fluctuaciones de reposo y su estadística son determinadas por la estructura de la red cerebral y su dinámica.
Koc, Seyma. "Categorical Effect Studied Through Fmri In Color Perception". Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614802/index.pdf.
Texto completoincreased activation in these regions is related to enhanced visual performance and higher scores, which is consistent with significantly better performance in within-green discrimination than cross-category discrimination. For the same contrast, Parahippocampal Gyrus and Precuneus activations suggest better visual recall and behavioral improvement due to more efficient maintenance in spatial working memory for within-green discrimination than cross-category discrimination. Brain activity differences reported in the within-blue condition versus cross-category condition is focused on Superior Temporal Gyrus, which is involved in color discrimination having the role of color memory. When within-green and within-blue conditions are compared, there was differential activation in the Fusiform Gyrus, and this is the only brain activity which might be attributed to a categorical effect. This comparison also yielded activity in Medial Frontal and Superior Frontal regions concerning more confident perceptual decisions and improved performance on within-green discrimination than within-blue discrimination. In addition, spatial separation of stimuli entailed more cognitive resources to color discrimination than adjacent stimuli as suggested by Cuneus and Lingual Gyrus activations. Overall, to the best of our knowledge our study is the first to investigate the neural framework for color perception, which revealed that color perception might involve several complex sub-processes that activate memory and attention.
Allievi, Alessandro. "Robot-assisted fMRI assessment of early brain development". Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/34342.
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