Localization of sources of brain alpha/theta/delta activity and the influence of the mode of spontaneous mentation

Abstract

A method is described that accounts for multichannel brain field data (EEG) epochs, after transformation into the frequency domain, by a single oscillating dipole source in terms of phase angles. The method produces a potential distribution for each frequency period (FFT dipole approximation). These maps can be subjected to conventional equivalent dipole source fittings in terms of amplitudes. The authors studied the equivalent source locations for the different temporal EEG frequency bands (delta/theta/alpha) in 12 normal subjects during the collection of reports of spontaneous thoughts. Some of the thought reports were classed into two modes, 'visual imagery' and 'abstract', and the associated equivalent source locations during the 2 s immediately prior to these reports were computed. Different equivalent source locations were found for the different spectral components of the EEG, implying that different neural generator populations generate the different frequencies.