RESUMO
The aim of this study was to explain the temporal variations between subjects in the blood oxygenation level-dependent (BOLD) response. Somatosensory responses were elicited with the electrical forepaw stimulus at a frequency of 10 Hz in urethane-anesthetized rats, and functional magnetic resonance imaging (fMRI) with BOLD contrast and local field potential (LFP) measurements were performed simultaneously. BOLD fMRI activation was evaluated by two different models, one based on the stimulus paradigm (the block model) and the other on the simultaneously measured evoked LFP responses. In the initial analysis, the LFP model captured the BOLD activation in the primary somatosensory cortex in all cases, and the block model in 10 of 12 rats. A statistical comparison of the two models revealed that the LFP-derived model was able to explain additional BOLD variation over the block model in the somatosensory cortex in nine of 12 rats. These results suggest that there is more information regarding neuronal activity in the BOLD signal than can be exploited using the block model alone. Furthermore, the hemodynamic coupling remains unchanged in the case of temporally variable BOLD signals.
Assuntos
Potenciais Somatossensoriais Evocados/fisiologia , Oxigênio/sangue , Córtex Somatossensorial/fisiologia , Animais , Estimulação Elétrica , Masculino , Ratos , Ratos Wistar , Fatores de TempoRESUMO
In this paper, we present a method for modeling human brain response using combined fMRI and EEG measurements. A subspace is formed using the eigenvectors of data correlation matrix of augmented measurements. This subspace is then used for regularization of the fitting of parametric model to fMRI BOLD signal. The approach is utilized for single-trial estimation of blood oxygenation level dependent (BOLD) responses in fMRI time series.
Assuntos
Algoritmos , Mapeamento Encefálico/métodos , Eletroencefalografia/métodos , Potenciais Evocados Visuais/fisiologia , Imageamento por Ressonância Magnética/métodos , Córtex Visual/fisiologia , Percepção Visual/fisiologia , Adulto , Humanos , Masculino , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
In this paper, we present a subspace approach for functional magnetic resonance imaging (fMRI) time series analysis. The signal subspace is formed of the eigenvectors of data correlation matrix. The approach is utilized both for single-trial estimation of blood oxygenation level dependent (BOLD) responses in fMRI time series and for studying the functional connectivity of BOLD responses from different spatial areas.
