Elevated noise power in gamma band related to negative symptoms and memory deficit in schizophrenia

BackgroundThere is an increasing consideration for a disorganized cerebral activity in schizophrenia, perhaps relating to a synaptic inhibitory deficit in the illness. Noise power (scalp-recorded electroencephalographic activity unlocked to stimuli) may offer a non-invasive window to assess this possibility.Methods29 minimally-treated patients with schizophrenia (of which 17 were first episodes) and 27 healthy controls underwent clinical and cognitive assessments and an electroencephalographic recording during a P300 paradigm to calculate signal-to-noise ratio and noise power magnitudes in the theta and gamma bands.ResultsIn comparison to controls, a significantly higher gamma noise power was common to minimally-treated and first episode patients over P3, P4, T5 and Fz electrode sites. Those high values were directly correlated to negative symptom severity and inversely correlated to verbal memory scores in the patients. There were no differences in signal-to-noise ratio magnitudes among the groups. Gamma noise power at Fz discriminated significantly between patients and controls. No significant differences were found in theta noise power or in gamma noise power over the other electrode sites between the groups of patients and controls.LimitationsWe have not assessed phase-locked and non-phase locked power changes, a complementary approach that may yield useful information.ConclusionsGamma noise power may represent a useful and non-invasive tool for studying brain dysfunction in psychotic illness. These results suggest an inefficient activation pattern in schizophrenia.

► Noise power is useful for studying disorganized brain activity in schizophrenia. ► We study clinical, cognitive and EEG data from patients and healthy controls. ► Patients displayed elevated gamma noise power at parietal-temporal areas. ► High scores in patients were correlated to negative symptoms and verbal memory. ► There seems to be an inefficient activation pattern in schizophrenia.