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From EEG to BOLD: Brain mapping and estimating transfer functions in simultaneous EEG-fMRI acquisitions

SATO, Joao R.; RONDINONI, Carlo; STURZBECHER, Marcio; ARAUJO, Draulio B. de; AMARO JR., Edson
Fonte: ACADEMIC PRESS INC ELSEVIER SCIENCE Publicador: ACADEMIC PRESS INC ELSEVIER SCIENCE
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.04%
Simultaneous acquisition of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) aims to disentangle the description of brain processes by exploiting the advantages of each technique. Most studies in this field focus on exploring the relationships between fMRI signals and the power spectrum at some specific frequency bands (alpha, beta, etc.). On the other hand, brain mapping of EEG signals (e.g., interictal spikes in epileptic patients) usually assumes an haemodynamic response function for a parametric analysis applying the GLM, as a rough approximation. The integration of the information provided by the high spatial resolution of MR images and the high temporal resolution of EEG may be improved by referencing them by transfer functions, which allows the identification of neural driven areas without strong assumptions about haemodynamic response shapes or brain haemodynamic`s homogeneity. The difference on sampling rate is the first obstacle for a full integration of EEG and fMRI information. Moreover, a parametric specification of a function representing the commonalities of both signals is not established. In this study, we introduce a new data-driven method for estimating the transfer function from EEG signal to fMRI signal at EEG sampling rate. This approach avoids EEG subsampling to fMRI time resolution and naturally provides a test for EEG predictive power over BOLD signal fluctuations...

Reconhecimento de estados cognitivos em sinas EEG.; Recognition of cognitive states in EEG signals.

Flores Vega, Christian Humberto
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 15/01/2010 PT
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36.94%
O processamento de sinais EEG permite interpretar, analisar, estudar, pesquisar e experimentar a atividade elétrica do cérebro como resposta para diferentes processos cognitivos, efeitos de drogas ou fármacos, estudo de doenças psiquiátricas ou neurológicas, entre outras. Esta dissertação é orientada ao reconhecimento de padrões cerebrais que permitam classificar estados cognitivos mediante os sinais de EEG registrados em sujeitos realizando tarefas programadas. Ademais espera-se obter a maior quantidade de padrões para cada estado cognitivo e procurar os parâmetros que oferecem maior informação, analisando as principais bandas cerebrais e todos os eletrodos disponíveis na base de dados. A metodologia usada compreende o registro de cinco tarefas cognitivas analisadas com três abordagens diferentes: análises de longe-range tenporal correlations com o algoritmo de Detrended Fluctuations Analysis (DFA), análise da potência dos sinais cerebrais utilizando a Transformada Ondeleta e finalmente o estudo da sincronia cerebral usando a Transformada de Hilbert. Conclui-se que as abordagens utilizadas nesta dissertação reportam alentadores resultados para diferenciar as tarefas cognitivas estudadas, demonstrando que a utilização da informação de todos os eletrodos e de suas principais bandas cerebrais contribuem de forma positiva. Também se consegue reconhecer e identificar quais parâmetros produzem maior informação para esta análise.; EEG signal processing allows interpreting...

Métodos clássicos  e alternativos para a análise de dados de fMRI e EEG-fMRI simultâneo em indivíduos assintomáticos, pacientes com epilepsia e com estenose carotídea; Classic and alternative methods for fMRI and simultaneous EEG-fMRI data analysis in asymptomatic subjects, patients with epilepsy and carotid stenosis

Sturzbecher, Marcio Junior
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 10/05/2011 PT
Relevância na Pesquisa
37.15%
O mapeamento das respostas BOLD (Blood Oxygenation Level Dependent) constitui etapa importante nos experimentos de imagem funcional por ressonância magnética (Functional Magnetic Resonance Imaging fMRI) e de EEG-fMRI simultâneo. Em sua grande maioria, a análise de dados de fMRI e de EEG-fMRI está baseada no modelo linear geral (General Linear Model GLM), que procura localizar as respostas BOLD por meio de modelos definidos a priori. Porém, em muitos casos, como em pacientes, variações na forma e/ou atraso podem reduzir a confiabilidade dos resultados. Desse modo, o primeiro objetivo deste trabalho foi explorar métodos clássicos e propor novos métodos para análise de dados de fMRI e de EEG-fMRI simultâneo. Neste trabalho, um método modificado baseado na distância de Kullback-Leibler generalizada (dKLg) foi desenvolvido. Diferentemente do GLM, essa abordagem não requer um modelo para a resposta. Dados simulados foram utilizados para otimizá-lo e compará-lo ao GLM sob diferentes condições de resposta como a relação sinal ruído e a latência. Em seguida, o dKLg foi testado em dados reais, adquiridos em 14 voluntários assintomáticos, submetidos a tarefas motoras e auditivas padrões. Os resultados mostram a equivalência entre o dKLg e o GLM. Em seguida...

Em busca da região epileptiforme em pacientes com epilepsia do lobo temporal: métodos alternativos baseados em fMRI e EEG-fMRI; Searching for epileptiform region in patients with temporal lobe epilepsy: alternative methods based on fMRI and EEG-fMRI

Pastorello, Bruno Fraccini
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 25/08/2011 PT
Relevância na Pesquisa
37.03%
A epilepsia do lobo temporal (ELT) é a forma mais comum de epilepsia e a mais resistente ao tratamento medicamentoso. Existem diversos tipos de drogas anti-epilépticas usadas no controle das crises. Entretanto, em alguns casos, esse tipo de tratamento não é eficaz e a cirurgia para remoção da zona epileptogênica (ZE) pode ser uma alternativa recomendada. A ZE é definida como aquela onde as crises são originadas. Trata-se de um conceito teórico e, atualmente, não existem técnicas capazes de delimitá-la precisamente. Na prática, exames de EEG, vídeo-EEG, MEG, SPECT, PET e diversas técnicas de MRI, em especial as funcionais, têm sido usados para mapear zonas relacionadas à ZE. Contudo, em alguns casos, os resultados permanecem não convergentes e a determinação da ZE inconclusiva. Desse modo, é evidente a importância do surgimento de novas metodologias para auxiliar a localização da ZE. Assim, pois, o objetivo deste trabalho foi desenvolver dois métodos para a avaliação da ZE, ambos baseados na imagem funcional por ressonância magnética. No primeiro, investigamos possíveis alterações da resposta hemodinâmica (HRF) quando da modulação da pressão parcial de CO2. Para tanto, fizemos um estudo sobre 22 pacientes com ELT e 10 voluntários assintomáticos modulando a pressão parcial de CO2 sanguíneo cerebral por um protocolo de manobra de pausa respiratória e outro de inalação passiva de CO2/ar. Os resultados mostram que o tempo de onset da HRF tende a ser maior e a amplitude da HRF tende a ser menor em áreas do lobo temporal de pacientes com ELT quando comparados com os dados de voluntários assintomáticos. Além disso...

Análise de wavelets com máquina de vetor de suporte no eletrencefalograma da doença de Alzheimer; Wavelets analysis with support vector machine in Alzheimer's disease EEG

Kanda, Paulo Afonso Medeiros
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 07/03/2013 PT
Relevância na Pesquisa
36.97%
INTRODUÇÃO. O objetivo deste estudo foi responder se a transformada wavelet Morlet e as técnicas de aprendizagem de Máquina (ML), chamada Máquinas de Vetores de Suporte (SVM) são adequadas para procurar padrões no EEG que diferenciem controles normais de pacientes com DA. Não há um teste de diagnóstico específico para a doença de Alzheimer (DA). O diagnóstico da DA baseia-se na história clínica, neuropsicológica, exames laboratoriais, neuroimagem e eletroencefalografia. Portanto, novas abordagens são necessárias para permitir um diagnóstico mais precoce e preciso e para medir a resposta ao tratamento. EEG quantitativo (EEGq) pode ser utilizado como uma ferramenta de diagnóstico em casos selecionados. MÉTODOS: Os pacientes eram provenientes do Ambulatório do Grupo de Neurologia Cognitiva e do Comportamento (GNCC) da Divisão de Clínica Neurológica do HCFMUSP ou foram avaliados pelo grupo do Laboratório de Eletrencefalografia Cognitiva do CEREDIC HC-FMUSP. Estudamos EEGs de 74 indivíduos normais (33 mulheres/41 homens, com idade média de 67 anos) e 84 pacientes com provável DA leve a moderada (52 mulheres/32 homens, idade média de 74,7 anos. A transformada wavelet e a seleção de atributos foram processadas pelo software Letswave. A análise SVM dos atributos (bandas delta...

The impact of EEG in the diagnosis and management of patients with acute impairment of consciousness

Ricardo, Joao A. G.; Franca, Marcondes C., Jr.; Lima, Fabricio O.; Yassuda, Clarissa L.; Cendes, Fernando
Fonte: Assoc Arquivos Neuro- Psiquiatria; Sao Paulo Publicador: Assoc Arquivos Neuro- Psiquiatria; Sao Paulo
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.94%
Objectives: To assess the frequency of electroencephalogram (EEG) requests in the emergency room (ER) and intensive care unit (ICU) for patients with impairment of consciousness (IC) and its impact in the diagnosis and management. Methods: We followed patients who underwent routine EEG from ER and ICU with IC until discharge or death. Results: During the study, 1679 EEGs were performed, with 149 (8.9%) from ER and ICU. We included 65 patients and 94 EEGs to analyze. Epileptiform activity was present in 42 (44.7%). EEG results changed clinical management in 72.2% of patients. The main reason for EEG requisition was unexplained IC, representing 36.3% of all EEGs analyzed. Eleven (33%) of these had epileptiform activity. Conclusion: EEG is underused in the acute setting. The frequency of epileptiform activity was high in patients with unexplained IC. EEG was helpful in confirming or ruling out the suspected initial diagnosis and changing medical management in 72% of patients.; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Comparison of Methods and Co-Registration Maps of EEG and fMRI in Occipital Lobe Epilepsy

Forjaz Secca, M; Leal, A; Cabral, J; Fernandes, H
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Conferência ou Objeto de Conferência
Publicado em //2007 ENG
Relevância na Pesquisa
36.99%
Clinically childhood occipital lobe epilepsy (OLE) manifests itself with distinct syndromes. The traditional EEG recordings have not been able to overcome the difficulty in correlating the ictal clinical symptoms to the onset in particular areas of the occipital lobes. To understand these syndromes it is important to map with more precision the epileptogenic cortical regions in OLE. Experimentally, we studied three idiopathic childhood OLE patients with EEG source analysis and with the simultaneous acquisition of EEG and fMRI, to map the BOLD effect associated with EEG spikes. The spatial overlap between the EEG and BOLD results was not very good, but the fMRI suggested localizations more consistent with the ictal clinical manifestations of each type of epileptic syndrome. Since our first results show that by associating the BOLD effect with interictal spikes the epileptogenic areas are mapped to localizations different from those calculated from EEG sources and that by using different EEG/fMRI processing methods our results differ to some extent, it is very important to compare the different methods of processing the localization of activation and develop a good methodology for obtaining co-registration maps of high resolution EEG with BOLD localizations.

Optimization of fMRI Processing Parameters for Simutaneous Acquisition of EEG/fMRI in Focal Epilepsy

Forjaz Secca, M; Fernandes, H; Cabral, J; Leal, A
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Conferência ou Objeto de Conferência
Publicado em //2008 ENG
Relevância na Pesquisa
36.97%
In the context of focal epilepsy, the simultaneous combination of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) holds a great promise as a technique by which the hemodynamic correlates of interictal spikes detected on scalp EEG can be identified. The fact that traditional EEG recordings have not been able to overcome the difficulty in correlating the ictal clinical symptoms to the onset in particular areas of the lobes, brings the need of mapping with more precision the epileptogenic cortical regions. On the other hand, fMRI suggested localizations more consistent with the ictal clinical manifestations detected. This study was developed in order to improve the knowledge about the way parameters involved in the physical and mathematical data, produced by the EEG/fMRI technique processing, would influence the final results. The evaluation of the accuracy was made by comparing the BOLD results with: the high resolution EEG maps; the malformative lesions detected in the T1 weighted MR images; and the anatomical localizations of the diagnosed symptomatology of each studied patient. The optimization of the set of parameters used, will provide an important contribution to the diagnosis of epileptogenic focuses...

Comparison of Methods and Co-Registration Maps of EEG and fMRI in Occipital Lobe Epilepsy

Forjaz Secca, M; Leal, A; Cabral, J; Fernandes, H
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Conferência ou Objeto de Conferência
Publicado em //2007 ENG
Relevância na Pesquisa
36.99%
Clinically childhood occipital lobe epilepsy (OLE) manifests itself with distinct syndromes. The traditional EEG recordings have not been able to overcome the difficulty in correlating the ictal clinical symptoms to the onset in particular areas of the occipital lobes. To understand these syndromes it is important to map with more precision the epileptogenic cortical regions in OLE. Experimentally, we studied three idiopathic childhood OLE patients with EEG source analysis and with the simultaneous acquisition of EEG and fMRI, to map the BOLD effect associated with EEG spikes. The spatial overlap between the EEG and BOLD results was not very good, but the fMRI suggested localizations more consistent with the ictal clinical manifestations of each type of epileptic syndrome. Since our first results show that by associating the BOLD effect with interictal spikes the epileptogenic areas are mapped to localizations different from those calculated from EEG sources and that by using different EEG/fMRI processing methods our results differ to some extent, it is very important to compare the different methods of processing the localization of activation and develop a good methodology for obtaining co-registration maps of high resolution EEG with BOLD localizations.

Optimization of fMRI Processing Parameters for Simutaneous Acquisition of EEG/fMRI in Focal Epilepsy

Forjaz Secca, M; Fernandes, H; Cabral, J; Leal, A
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Conferência ou Objeto de Conferência
Publicado em //2008 ENG
Relevância na Pesquisa
36.97%
In the context of focal epilepsy, the simultaneous combination of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) holds a great promise as a technique by which the hemodynamic correlates of interictal spikes detected on scalp EEG can be identified. The fact that traditional EEG recordings have not been able to overcome the difficulty in correlating the ictal clinical symptoms to the onset in particular areas of the lobes, brings the need of mapping with more precision the epileptogenic cortical regions. On the other hand, fMRI suggested localizations more consistent with the ictal clinical manifestations detected. This study was developed in order to improve the knowledge about the way parameters involved in the physical and mathematical data, produced by the EEG/fMRI technique processing, would influence the final results. The evaluation of the accuracy was made by comparing the BOLD results with: the high resolution EEG maps; the malformative lesions detected in the T1 weighted MR images; and the anatomical localizations of the diagnosed symptomatology of each studied patient. The optimization of the set of parameters used, will provide an important contribution to the diagnosis of epileptogenic focuses...

Valor do EEG na caracterização e prognóstico de patologias neurológicas em recém-nascidos prematuros

Nunes,Magoa Lahorgue; Costa,Jaderson Costa da; Taufer,Letícia; Silveira,Claudia Marisa Duro da
Fonte: Academia Brasileira de Neurologia - ABNEURO Publicador: Academia Brasileira de Neurologia - ABNEURO
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/1995 PT
Relevância na Pesquisa
36.97%
A importância do EEG na investigação de patologias neurológicas no período neonatal tem sido discutido com frequência na atualidade, pois muitas vezes este é o único meio de avaliar a função cerebral em recém-nascidos (RN) com patologias graves ou sob efeito de medicações. O presente estudo foi realizado com 85 RN prematuros que apresentaram patologias neurológicas no período neonatal e foram submetidos a avaliação neurológica e eletrencefalográfica (EEG ou polissonografia -PS). Foram relacionadas alterações do EEG, patologias e prognóstico. Os EEGs foram classificados segundo as alterações da atividade de base, presença de atividade paroxística, organização dos estágios do sono e "maturidade". A patologia mais frequente foi asfixia perinatal (40%), seguida de hemorragia intra-ventricular (HIV, 16%). A queixa mais frequente na indicação do exame foi apnéia (71 %), seguida de convulsões (19%). Foram considerados normais 55% dos exames solicitados com queixa exclusiva de apnéia; dos exames solicitados por convulsões somente 31 % foram normais. A alteração do EEG mais frequentemente encontrada nos RN com asfixia, HIV e desnutrição intra-uterina foi a "imaturidade" da atividade elétrica cerebral. Nos RN com convulsões as alterações mais frequentes do EEG foram atividade paroxística anormal e "imaturidade". Os RN com infecção do sistema nervoso central apresentaram diversas alterações no EEG. Os achados de EEG mais correlacionados a mau prognóstico foram isoeletricidade e atividade paroxística anormal (100% dos casos com presença de ondas agudas positivas).

EEG recording after sleep deprivation in a series of patients with juvenile myoclonic epilepsy

Sousa,Nise Alessandra de Carvalho; Sousa,Patrícia da Silva; Garzon,Eliana; Sakamoto,Américo C.; Braga,Nádia I.O.; Yacubian,Elza Márcia Targas
Fonte: Academia Brasileira de Neurologia - ABNEURO Publicador: Academia Brasileira de Neurologia - ABNEURO
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2005 EN
Relevância na Pesquisa
37.04%
Seizures in Juvenile Myoclonic Epilepsy (JME) are dependent on the sleep-wake cycle and precipitant factors, among which sleep deprivation (SD) is one of the most important. Still an under diagnosed syndrome, misinterpretation of the EEGs contributes to diagnostic delay. Despite this, a quantitative EEG investigation of SD effects has not been performed. We investigated the effect of SD on EEGs in 41 patients, aged 16-50 yr. (mean 25.4), who had not yet had syndromic diagnosis after a mean delay of 8.2 yr. Two EEG recordings separated by a 48-hour interval were taken at 7 a.m. preceded by a period of 6 hours of sleep (routine EEG) and after SD (sleep-deprived EEG). The same protocol was followed and included a rest wakefulness recording, photic stimulation, hyperventilation and a post-hyperventilation period. The EEGs were analyzed as to the effect of SD on the number, duration, morphology, localization and predominance of abnormalities in the different stages. A discharge index (DI) was calculated. Out of the 41 patients, 4 presented both normal EEG recordings. In 37 (90.2%) there were epileptiform discharges (ED). The number of patients with ED ascended from 26 (70.3%) in the routine EEG to 32 (86.5%) in the sleep-deprived exam. The presence of generalized spike-wave and multispike-wave increased from 20 (54.1%) and 13 (35.1%) in the first EEG to 29 (78.4%) and 19 (51.4%) in the second...

Neurofeedbacktherapie bei Kindern mit einer Aufmerksamkeitsdefizit-Hyperaktivitäts-Störung: Zusammenhänge zwischen den langsamen kortikalen Potenzialen und dem EEG-Frequenzspektrum; Neurofeedback therapy for Children with Attention Deficit Hyperactivity Disorder: Relationship between Slow Cortical Potentials and EEG Frequency Spectrum

Rumpf, Nicola
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
Relevância na Pesquisa
37.08%
Diese Arbeit ist Teil einer Studie, in der zwei verschiedene Neurofeedbacktherapien untersucht wurden. Die Stichprobe bestand aus 36 Kindern im Alter von 8 bis 13 Jahren mit ADHS oder ADS nach den DSM-IV-Kriterien, die randomisiert und parallelisiert den zwei Therapiegruppen zugeteilt wurden. Der einen Gruppe wurden ihre langsamen Potenziale zurückgemeldet (LP-Kinder), der anderen Gruppe ihre Theta- und Beta-Aktivität in Form des Theta/Beta-Quotienten (QT-Kinder). In beiden Gruppen erfolgte das Feedback akustisch und optisch. Das Therapieprogramm bestand aus insgesamt 35 Sitzungen mit je 4 Durchgängen, wobei in jedem Durchgang 38 bis 40 Aufgaben dargeboten wurden. Eine Aufgabe war es den zurückgemeldeten EEG-Parameter gegenüber der Baseline zu verkleinern (Aktivierungsaufgabe), die andere diesen zu vergrößern (Deaktivierungsaufgabe). In dieser Arbeit wurde überprüft, ob das Feedback des einen EEG-Parameters zu Veränderungen des anderen EEG-Parameters führte, bzw. ob mit Veränderungen des einen EEG-Parameters Veränderungen des anderen EEG-Parameters einhergingen. Um diese Frage zu beantworten, wurden die Sitzungen 21 bis 30 auf Veränderungen im jeweils nicht zurückgemeldeten EEG-Parameter untersucht. Hierbei wurden nur bei der Untergruppe von LP-Kindern...

Autoantikörper und EEG-Befunde bei Patienten mit verschiedenen psychiatrischen Erkrankungen; Autoantibodies and EEG-findings in patients with different psychiatric disorders

Wehrle, Regina
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
Relevância na Pesquisa
36.99%
Demenzerkrankungen, depressive Störungen und andere psychiatrische Erkrankungen stellen zunehmende Diagnosen in unserer Gesellschaft dar. Daher wird ihre exakte und schnelle Diagnose und die möglichst genaue Aussage über Verlauf und Schweregrad immer bedeutender. Es bedarf aus diesem Grund neben den etablierten Diagnosekriterien neuer Diagnoseparameter, welche die vorhandenen sinnvoll ergänzen und eine noch exaktere Diagnose bzw. eine Aussage über Prognose und Verlauf ermöglichen. In dieser Arbeit wurde untersucht, ob Patienten mit Demenzerkrankungen, depressiven Störungen oder anderen psychiatrischen Erkrankungen Veränderungen in EEG oder in einem durchgeführten immunpathologischen Labor aufweisen. Ferner wurden verschiedene Autoantikörper analysiert und ein EEG-Befund erhoben. Außerdem wurden die Entzündungszeichen bestimmt. Es zeigte sich, dass bei den Patienten mit diesen Erkrankungen regelhaft Auffälligkeiten sowohl im EEG, als auch im immunpathologischen Labor gefunden werden können. Diese Veränderungen kommen auch in der Allgemeinbevölkerung vor – besonders bei älteren Patienten –, ohne einen Krankheitswert zu erreichen; dennoch können sie in Kombination mit den untersuchten Erkrankungen, wie Depression und Demenzerkrankungen möglicherweise ein weiterer Baustein in der Diagnostik sein und ihr Auftreten kann womöglich Aussagen über Schwere der Erkrankung...

EEG-correlates of coordinate processing during intermanual transfer; EEG-correlates of coordinate processing during intermanual transfer; EEG-Korrelate der Koordinatenprozessierung während des intermanuellen Transfers

Lange, Regine Kerstin
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
EN
Relevância na Pesquisa
36.99%
Acquisition of sensorimotor skill facilitates performance of the identical and mirror reversed task with the opposite hand (Normal-task and Mirror-task) The specific control of the Normal- task and Mirror-task can be conceived as a specific use of learned information in different coordinate systems. Intrinsic, body-related coordinates are preserved in the Mirrortask, but must be transformed in the Normal-task. Extrinsic, object-centred coordinates are modified in the Mirror-task, but not in the Normal-task. To identify the neuronal correlates of coordinate processing during intermanual transfer, EEG-recordings were obtained during the repetition of a trained drawing task (Learned-task) and the performance of the Normal-task and Mirror-task with the opposite hand. Behavioural data showed transfer effects in each task. As compared to the right-handed Learned-task, the left-handed Normal-task revealed increases of negativity in movementrelated potentials and EEG-power and a decrease of EEG-coherence prior to movement onset. The Mirror-task did not differ in general from the Learned-task. After left-handed training, beta-coherence increased in the Mirror-task relatively to the Learned-task after movement onset, whereas the Normal-task did not differ from the Learned-task. The results indicate that right-handed skill is transferred in intrinsic coordinates which code for movement preparation. The transfer of left-handed skill occurs in extrinsic coordinates which control the actually executed task. The modification of intrinsic coordinates induces increased activity of cortical areas and a decrease of inter-regional communication. Increases of inter-regional information exchanges...

Functional brain imaging on mobile devices by solving the EEG inverse problem: a structured sparsity approach

Montoya Martínez, Jair
Fonte: Universidade Carlos III de Madrid Publicador: Universidade Carlos III de Madrid
Tipo: Tese de Doutorado
ENG
Relevância na Pesquisa
37.09%
In this thesis we address the development of a mobile brain scanner, which is based on a wireless EEG neuroheadset, in charge of acquiring and transmitting the electrical potential measured on the scalp, and one mobile device (smartphone or tablet), in charge of receiving and processing these data to produce the cortical activation maps, which show, using a 3D brain model, the brain areas that are currently active. To generate the cortical activation maps, the mobile brain scanner needs to solve an electromagnetic inverse problem called the EEG inverse problem. The low spatial resolution of the EEG caused by the low conductivity of the skull plus the small number of EEG sensors available to capture the electrical activity produced by thousands of brain current sources, imply that the EEG inverse problem is underdetermined, ill-posed, and has infinite solutions. To make this problem tractable, in this thesis we assume that the number of active sources is small, that is, we assume that the set of active sources is a sparse set. Additionally, we also assume a linear relationship between the elements of this set. If we represent the set of brain current sources as a matrix (called the sources matrix), where the rows denote how the electrical activity of the sources vary over time...

Neural substrates of 2D/3D object perception: a combined EEG/fMRI approach

Castelhano, João Miguel Seabra
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Tese de Doutorado
ENG
Relevância na Pesquisa
37.01%
Perceptual decision making is defined as the choice of possible interpretations of the world based on the incoming sensory evidence. The role of temporal coding in this process and coherent perception, defined as hierarchical grouping of local elements, remains controversial. Oscillatory processes in the gamma frequency range (>30 Hz) have been proposed to play a role in signaling emerging object percepts in the brain. Studies using Electroencephalography and Magnetoencephalography (EEG and MEG) have suggested that gamma-band oscillations are related to the integration of information and the ability to form coherent gestalts as well as attention and working memory processes. It is accepted that gamma-band synchrony reflects binding of information across different brain regions leading to the emergence of a coherent percept. There are also reports that correlate gamma activity with many other cognitive processes. Hence, a wide variety of gamma-band patterns and sources were reported for different tasks. In this line, both animal and human studies have suggested that understanding oscillatory activity patterning can be important to understand normal and abnormal cognitive function. However, it remains unclear whether distinct patterns across the gamma frequency range related to different cognitive modules do coexist in the same task. We investigated visual perceptual recognition moments based on EEG analysis with ambiguous Mooney stimuli (black and white incomplete pictures). We departed from classical paradigms which are based on contrasts between stimuli conditions that are fixed in time...

EEG Frequency Band Power and Pupil Dilation as Measures for Executive Working Memory Load in Task Settings of Basic and Applied Research

Scharinger, Christian
Fonte: Universität Tübingen Publicador: Universität Tübingen
Tipo: Dissertation; info:eu-repo/semantics/doctoralThesis
EN
Relevância na Pesquisa
37.09%
Performing a task, for example the selection of links during hypertext reading, raises cognitive demands, that is, induces cognitive load. Cognitive load may be attributed to working memory (WM) functioning. Core executive functions (EFs), like updating, shifting, and inhibition, may define the executive (i.e., working) part of WM and thus may be essential for WM functioning. Consequently, cognitive load may result out of the demands on core EFs during task performance. Brain oscillatory activity as captured in the electroencephalogram (EEG) by frequency band power in time-frequency representations (TFRs) might serve as a measure for demands on core EFs. Especially, EEG alpha frequency band power could serve as a global measure of the cognitive load-situation which grounds in demands on core EFs. Pupil dilation, which can be more efficiently acquired as compared to the EEG, might also be used as a measure of the overall load-situation. Yet, the role of core EFs for WM functioning has been rarely studied to date, and the interplay of core EFs and their relation to WM is still matter of debate. Most important, the use of the physiological measures EEG alpha frequency band power and pupil dilation for assessing demands on core EFs and the global cognitive load-situation in complex...

Joint Coupling of Awake EEG Frequency Activity and MRI Gray Matter Volumes in the Psychosis Dimension: A BSNIP Study

Soh, Pauline; Narayanan, Balaji; Khadka, Sabin; Calhoun, Vince D.; Keshavan, Matcheri S.; Tamminga, Carol A.; Sweeney, John A.; Clementz, Brett A.; Pearlson, Godfrey D.
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
EN_US
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Background: Many studies have examined either electroencephalogram (EEG) frequency activity or gray matter volumes (GMV) in various psychoses [including schizophrenia (SZ), schizoaffective (SZA), and psychotic bipolar disorder (PBP)]. Prior work demonstrated similar EEG and gray matter abnormalities in both SZ and PBP. Integrating EEG and GMV and jointly analyzing the combined data fully elucidates the linkage between the two and may provide better biomarker- or endophenotype-specificity for a particular illness. Joint exploratory investigations of EEG and GMV are scarce in the literature and the relationship between the two in psychosis is even less explored. We investigated a joint multivariate model to test whether the linear relationship or linkage between awake EEG (AEEG) frequency activity and GMV is abnormal across the psychosis dimension and if such effects are also present in first-degree relatives. Methods: We assessed 607 subjects comprising 264 probands [105 SZ, 72 SZA, and 87 PBP], 233 of their first degree relatives [82 SZ relatives (SZR), 71 SZA relatives (SZAR), and 80 PBP relatives (PBPR)], and 110 healthy comparison subjects (HC). All subjects underwent structural MRI (sMRI) and EEG scans. Frequency activity and voxel-based morphometric GMV were derived from EEG and sMRI data...

TMS-EEG combined with granger causality: an innovative information flow approach over the full brain connectivity

Fernandes, Tiago José Cardoso Pires Timóteo
Fonte: Universidade de Lisboa Publicador: Universidade de Lisboa
Tipo: Dissertação de Mestrado
Publicado em //2015 ENG
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Tese de mestrado integrado em Engenharia Biomédica e Biofísica, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2015; Atualmente, no mundo das neurociências, a conectividade cerebral é um tema em destaque. Este conceito encontra-se dividido em conetividade estrutural (relações anatómicas entre estruturas cerebrais), conectividade funcional (dependências estatísticas entre estruturas cerebrais) e conectividade efetiva (relações de causalidade entre estruturas cerebrais). Esta tese debaterá fundamentalmente sobre o último destes conceitos, tentando oferecer uma interpretação para o fluxo de informações entre as áreas do cérebro. Muitas técnicas podem ser utilizadas na sua análise, entre os quais a Causalidade de Granger (GC) ou a estimulação magnética transcraniana em combinação com eletroencefalografia (TMS-EEG). Por um lado, a GC permite uma interpretação das ligações diretas dentro e fora das mesmas áreas cerebrais, sendo uma abordagem explicativa sobre os dados, onde não é necessária nenhuma hipótese sobre o comportamento das relações causais. No entanto, os resultados de GC são muito sensíveis, uma vez que dependem de sinais não-estacionários e não colineares, aspetos bastante presentes em sinais de eletroencefalografia (EEG). Desta forma...