Do high or low doses of anxiolytics and hypnotics affect mismatch negativity in schizophrenic subjects? An EEG and MEG study

OBJECTIVE Many studies have demonstrated mismatch negativity (MMN) attenuation in schizophrenia. Recently, investigators have shown that GABAergic inhibitory neurons may regulate MMN generation. Considering that a substantial proportion of schizophrenic patients receive anxiolytics and hypnotics that have affinity to GABA(A) receptors to reduce their comorbid symptoms of anxiety and sleep disturbances, we need to assess whether anxiolytics/hypnotics might affect their MMN generation. The aim of this study is to assess the possibility that high or low doses of anxiolytics/hypnotics received by schizophrenic subjects affect their mismatch negativity (MMN), using event-related potentials (ERPs) and magnetoencephalography (MEG). METHODS Twenty-three and 16 patients with schizophrenia participated in the ERP and MEG studies, respectively. Three types of MMN (MMN in response to a duration change of pure-tone stimuli, within-category vowel change (Japanese vowel /a/ with short versus long duration), and across-category vowel change (vowel /a/ versus /o/)) were recorded. RESULTS High or low doses of benzodiazepine had no significant effects on MMN amplitude/magnetic MMN power, topography/laterality, or latency under any conditions of the ERP or MEG study. CONCLUSIONS These results suggest that chronic administration of anxiolytics/hypnotics does not significantly affect MMN in schizophrenia.