High-Resolution Spatiotemporal Brain Functional Imaging Using Equivalent Dipole Layer

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In the present study, we explore suitable spatio-temporal filters for inverse estimation of an equivalent dipole-layer distribution from the scalp EEG for imaging of brain electric sources. We propose a time-varying parametric projection filter (tPPF) for the spatio-temporal EEG analysis. Concretely, the regularization parameter and the noise covariance of the PPF were adjusted according to the signal and noise conditions. The performance of this tPPF algorithm was evaluated by computer simulation and human experimental studies. An inhomogeneous three-concentric-spheres model was used in the present simulation study to represent the head volume conductor. An equivalent dipole layer was used to represent equivalently brain electric sources and estimated from the scalp potentials. The tPPF filter was tested to remove time-varying noise such as instantaneous artifacts caused by eyes-blink. The present simulation results indicate that the proposed time-variant tPPF method provides enhanced performance in rejecting time-varying noise, as compared with the time-invariant parametric projection filter. Human experiments of visual evoked potential showed that the proposed method localized noise. Further investigations on other applications of this new method should be addressed in the future.