Increased spontaneous gamma power and synchrony in schizophrenia patients having higher minor physical anomalies.

The higher frequency of minor physical anomalies (MPAs) in schizophrenia provides morphological evidence for the neurodevelopmental theory. Abnormal gamma oscillations (>30 Hz) seen in the electroencephalogram (EEG) in schizophrenia have been hypothesized to result from developmental insults. This study investigated spontaneous gamma oscillations in schizophrenia patients having higher and lower number of MPAs. Forty drug naïve/free schizophrenia patients and 20 matched healthy controls were assessed for MPAs on the Extended Waldrop Scale (EWS). All participants underwent an awake, resting 192-channel EEG recording. Spontaneous gamma spectral power and coherence were estimated in the low- (30-50 Hz) and high-gamma (51-70 and 71-100 Hz) bands. Significantly higher power was observed in high-MPA than healthy control group in low-gamma band over right frontal, parietal and temporal regions. Spectral power in the high-gamma band (71-100 Hz) was also significantly higher in the high-MPA schizophrenia subgroup than in the healthy control group over left frontal, parietal and temporal regions. Additionally, regional intra-hemispheric and inter-hemispheric coherence in the low-gamma band was significantly higher in the high-MPA schizophrenia subgroup than on the healthy control group. This study is the first to provide evidence of increased spontaneous gamma power and synchrony in schizophrenia patients having higher MPAs, supporting the idea that it may represent a distinct subgroup of schizophrenia with a neurodevelopmental basis.