Transcranial magnetic stimulation on the modulation of gamma oscillations in schizophrenia

Cognitive dysfunction is suggested to be the best predictor of functional outcome in schizophrenia. Therefore, new diagnostic and treatment strategies are needed to both ascertain the biological underpinning of cognitive deficits and to restore them. Modulation of gamma oscillations (30-50 Hz) has been associated with cognitive performance, particularly in the dorsolateral prefrontal cortex (DLPFC). In this manuscript, we review evidence for gamma modulation deficits during cognitive performance in schizophrenia. We demonstrate that transcranial magnetic stimulation (TMS) combined with electroencephalography (EEG) is a reliable method that permits systematic quantification of gamma modulation in the cortex. Using TMS-EEG, we show that patients with schizophrenia have selective gamma inhibition deficits in the DLPFC. Finally, we demonstrate that repetitive TMS therapy over the DLPFC can normalize excessive gamma oscillations and ultimately cognitive performance in patients. We suggest that restoring gamma impairments in the DLPFC may be a potential strategy for improving cognitive deficits in schizophrenia.