[A search for the sources of pathological alpha activity in the human EEG in limbic structure lesions]

Dependence of manifestations of EEG pathological activity on the electrode montage was studied in cases of brain lesions involving limbic structures by means of the topographic mapping and 3-d dipole source localization. The original program DIPVIS on the basis of BRAINLOC software allowed us to reveal the stable sources of lateralized pathologic alpha activity and demonstrate the discrepancy between its localization and the localization of the normal human alpha rhythm. The sources of pathological activity in question were predominantly localized in the mediobasal structures of the affected hemisphere in contrast to the occipital region of a healthy human. It was established that the topography of the cortical pathological activity may be determined by peculiarities of localization and, especially, orientation of its dipole generators. Afferent stimulation produced an enhancement of the pathological alpha-activity and increase in dipole source concentration in the mediobasal portion of the temporal lobe. The findings suggest that the discovered from of the alpha-rhythm reflects the reaction of activation of the hippocampal structures involved in the pathological process.