[Trajectories of alpha rhythm dipoles shifting over the human brain cortex]

Dynamic study of 3D localization of the equivalent current dipoles (ECD)--sources of the EEG alpha rhythm in the human brain was performed in seven subjects with closed eyes using a one-dipole model. An exact localization of ECDs was obtained by combination of EEG and MRI mapping that allowed tracing of ECD shifts over the cortex with 4 ms step. Our data confirmed localization of these ECDs mainly in the occipital cortex and revealed their successive shift over this area during generation of each alpha-wave. Typical trajectories of these shifts were revealed and quantitatively compared by the hierarchical cluster analysis. The data obtained directly proved periodical rhythmic alpha-wave spreading process in the human visual cortex and an external control of this process. The data are discussed in terms of the "scanning hypothesis" (Pitts W., McCulloch W.H. Bull. Math. Biophys. 1947. V. 9. P. 127) which predicted a certain functional meaning of the alpha activity for cortical processing of sensory information in the human brain.