Electro/Magnetoencephalography Signal Processing Methods and Performance

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Electro/MagnetoencephalographySignal Processing Methods and PerformanceArye NehoraiEECS DepartmentUniversity of Illinois at ChicagoDetecting electric sources in the brain is important for both understanding its function and for clinical applications. Examples include mapping the brain activities and finding foci of epilepsy activities before surgical treatment. We are developing detection methods that find the sources through computer processing of measurements from arrays of sensors around the head. More specifically, we employ Electro/Magnetoencephalography (E/MEG) sensors that measure electric potentials on the scalp and induced magnetic field outside the head. We are developing several new methods of processing the E/MEG signals, analyzing their performance and validating with real data their applicability, thus contributing to improvements in the use and performance of E/MEG equipment and to increase the capabilities of neurological data processing tools.We hope to solve some of the most currently relevant E/MEG problems: (i) estimating and tracking paths of functional and neuronal connectivity, following the trajectories of cerebral sources, (ii) estimating concentrated and extended sources, in the presence of noise with unknown spatio-temporal covariance, (iii) simultaneously estimating source parameters and tissue conductivities, (iv) developing computationally efficient methods for realistically-shaped head models, which reduce the demands on segmentation algorithms, (v) estimating source parameters for evoked responses with inhomogeneous epochs. We are also deriving performance measures for evaluating the newly proposed methods allowing comparison with existing systems and techniques; identifying those that are effective and helping in the optimum design of future systems. Finally, we are using empirical data sets evaluate and validate methods. These data sets are being derived by the Dr. Jeffrey Lewine's group from Clinical and Cognitive Neurosciences studies where whole-head MEG and high-density EEG are recorded simultaneously. The Nehorai group is developing the processing methods and the two groups will collaborate on their evaluation and validation.