Equivalent EEG sources determined by FFT approximation in healthy subjects, schizophrenic and depressive patients.

In recent years, as a result of increasing calculation power of computers and with the aid of appropriate computer programs it has been made possible to calculate equivalent dipoles as intracranial representations of cerebral electrical activity. The present study investigated the localization of intracerebral equivalent dipoles in healthy controls and psychiatric patients. The equivalent dipole sources were calculated for conventional frequency bands of the background EEG. This was performed using the FFT approximation by Lehmann and Michel. Results showed more anterior equivalent sources for alpha and beta activity in all patients compared to controls. The beta activity was also generated in deeper brain structures in controls compared to patients. These results indicate that frequency bands may be generated in different brain structures in patients suffering from psychiatric diseases as compared to healthy controls and that the calculation of equivalent dipole sources may be a way to perform a sensible and substantial data reduction.