Magnetoencephalographic gamma power reduction in patients with schizophrenia during resting condition

The "default network" represents a baseline condition of brain function and is of interest in schizophrenia research because its component brain regions are believed to be aberrant in the disorder. We hypothesized that magnetoencephalographic (MEG) source localization analysis would reveal abnormal resting activity within particular frequency bands in schizophrenia.

Eyes-closed resting state MEG signals were collected for two comparison groups. Patients with schizophrenia (N = 38) were age-gender matched with healthy control subjects (N = 38), and with a group of unmedicated unaffected siblings of patients with schizophrenia (N = 38). To localize 3D-brain regional differences, synthetic aperture magnetometry was calculated across established frequency bands as follows: delta (0.9-4 Hz), theta (4-8 Hz), alpha (8-14 Hz), beta (14-30 Hz), gamma (30-80 Hz), and super-gamma (80-150 Hz). PRINCIPLE OBSERVATIONS: Patients with schizophrenia showed significantly reduced activation in the gamma frequency band in the posterior region of the medial parietal cortex. As a group, unaffected siblings of schizophrenia patients also showed significantly reduced activation in the gamma bandwidth across similar brain regions. Moreover, using the significant region for the patients and examining the gamma band power gave an odds ratio of 6:1 for reductions of two standard deviations from the mean. This suggests that the measure might be the basis of an intermediate phenotype.

MEG resting state analysis adds to the evidence that schizophrenic patients experience this condition very differently than healthy controls. Whether this baseline difference relates to network abnormalities remains to be seen.