Spatial structure of brain electric fields during intermittent photic stimulation

EEG changes in 27 young healthy male right-handed volunteers on intermitten t photic stimulation (IPS) were estimated using global field power (GFP), E EG microstate modeling and analysis (EMMA), and low-resolution electromagne tic brain tomography (LORETA). The GFP significantly increased at flashing frequency and high harmonics. Three model maps were extracted with the EMMA procedure, from which high alternation rates of each microstate were obser ved. Moreover, two of the three model maps contributed very highly, occurri ng most frequently. LORETA imaging of the three model maps obtained from th e EMMA procedure showed that both visual dominant cortical areas were activ ated, especially in the left hemisphere. These results suggest that IPS doe s not cause peculiar spatial configurations of the brain electric field, bu t does cause acceleration and deviation of the microstate alternation. Also , a functional laterality between hemispheres might be enhanced by symmetri c IPS. Copyright (C) 2001 S. Karger AG, Basel.