A parametric model for multichannel EEG spectra.
The EEG is modelled as the superposition of two component processes: the xi and the alpha processes. In the frequency domain, the xi process is always present and appears as a spectral peak with maximum amplitude at very low frequencies, while the alpha process is characterized by a spectral peak with its maximum located in the traditional alpha band (7-13 Hz), and is not necessarily always present. The multivariate properties of EEG spectra are adequately modelled with frequency independent coherence matrices for each process. Multichannel EEG studies reveal interesting properties: (1) the generalized coherence for alpha is much larger than for xi, indicating increased functional coupling for the alpha process; (2) the alpha coherence matrix has reduced dimensionality, possibly related to a small number of generators; (3) xi coherences are zero phase with magnitudes that decrease exponentially with interelectrode distance; and (4) alpha coherences have significant nonzero phase shifts.
Pascual-Marqui
R D
RD
Neurosciences Branch, National Center for Scientific Research, Havana, Cuba.
Valdes-Sosa
P A
PA
Alvarez-Amador
A
A
D000465:Algorithms; D002648:Child; D002675:Child, Preschool; D004569:Electroencephalography; D006801:Humans; D008959:Models, Neurological; D012016:Reference Values