Diazepam and sulpiride effects on frequency domain EEG source locations

Effects of an anxiolytic (diazepam; n = 13) and an antipsychotic (sulpiride; n = 6) on the location of EEG model sources in the frequency domain were studied in normal volunteers in 19-channel eyes-closed EEG before and 1, 15, 30, 45 and 60 min after i.v. injections. Ten 2-second epochs from each recording were subjected to the fast Fourier transformation (FFT) Dipole Approximation which results in a single-source (in terms of phase angle) potential distribution map for each frequency point. Three-dimensional model dipole sources were fitted into the maps. Differences in source location before and after injection were computed, and differences between drugs were evaluated. The source location in the beta band shifted significantly more towards superior and anterior areas after diazepam than sulpiride, most prominently in the first minute after injection; during this time, conventional beta band power was significantly increased after diazepam versus sulpiride at all recording sites. The results demonstrate that the FFT dipole approximation adds direct 3-dimensional topographical information to power spectral results in pharmaco-EEG.