The interplay of lorazepam-induced brain oscillations:: microstructural electromagnetic study

Objective: The effects on cortical rhythms of a single-dose (30 mug/kg) administration of the GABA(A) agonist lorazepam were examined in a randomized, double-blind, cross-over, placebo-controlled study with 8 healthy volunteers using simultaneous electroencephalography (EEG) and magnetoencephalography (MEG). Methods: The oscillations were assessed by means of adaptive classification of short-term spectral patterns. Results: Lorazepam (a) decreased the percentage of EEG/MEG segments with fast-theta, delta-alpha, fast-theta-alpha and alpha activity and increased percentage of EEG/MEG segments with delta, delta-slow-theta, delta-beta, slow-theta and polyrhythmic activity; (b) decreased diversity of EEG/MEG signals (in terms of spectral patterns) and increased the general instability of the signal; (c) increased stabilization periods of the spectral patterns (reduced brain information processing); (d) maintained larger maximum periods of temporal stabilization for delta, slow-theta, delta-slow-theta, delta-beta and polyrhythmic activity (in terms of spectral patterns); (e) did not increase power in the independent beta rhythm. Conclusions: Lorazepam caused significant reorganization of the EEG/MEG microstructure. These results suggest also that adaptive classification analysis of single short-term spectral patterns may provide additional information to conventional spectral analyses. (C) 2003 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.