Electrical Source Imaging in Rats: Cortical EEG Performance and Limitations

The goal of the present work is to estimate electric activity within the brain volume based on measured potentials on the rats brain surface. At first, we calculated and analyzed sensitivity volume profile of cortical electrode pairs to address the cortical electrode positioning. Sensitivity volume profiles change rapidly with decreasing of expected minimal depth of the sources. Moreover, the profiles become unreliable in case of very small expected minimal depths, which is, unfortunately, the case of cortical electroencephalogram (EEG). This result was obtained in both analytical and numerical models. Second, appropriate regularization and normalization routines were implemented for minimum norm estimate and beam-forming methods. Third, the inverse methods were applied to localize simulated brain deep sources based on the twelve electrode cortical EEG system.