Equivalent dipole tracing of human alpha activities

The neural sources of human EEG electroencephalograph alpha activities have been investigated by an equivalent dipole fitting algorithm which takes the head shape into account. Two minutes of EEG were measured at 21 sites on the scalps of four young, healthy subjects. Single-moving-dipole fitting was performed, and a measure called proximity was introduced to evaluate the goodness of fit. The two-moving-dipole model was found to model the human alpha field very well. The equivalent dipoles are located symmetrically in both hemispheres when the amplitude of the mean squared field is large, and they change orientation over time. The results confirm previous findings that there may be multiple sources of alpha waves.