Cross-spectral and cross-bispectral analysis of hippocampal EEG with ICA processing

Hippocampal EEG collected from CA1 and the dentate gyrus during REM sleep were examined using linear cross-spectral and nonlinear cross-bispectral analysis to quantify the correlation between the two sites. Independent component analysis (ICA) was applied to remove any cocktail party effects that may exist between the recordings from the two hippocampal subfields. Cross-spectrum and cross-bispectrum of the EEG were computed before and after the ICA process to examine its effects. It was found that ICA almost completely removes the linear relationship in the theta frequency band between CA1 and the dentate gyrus. ICA processing also significantly reduces the quadratic phase coupling (QPC) observed between these two sites.