Patients were compared to 15 age and sex-matched healthy controls. Both average and maximum amplitude of absolute gamma (37-41Hz) synchrony were measured, and differences between groups were calculated using independent samples t-tests. Due to sample size limitations, stability of gamma synchrony was assessed as a mean change at follow-up that was within one-half of the baseline standard deviation. Correlational analyses were then conducted on the change in PANSS scores and change in gamma synchrony between sessions. At baseline and follow-up, a trend for raised gamma synchrony was observed in the psychosis group compared to controls.
Stability of gamma synchrony was observed across all regions despite a significant improvement in symptoms. In the left-frontal region, there was a significant positive correlation between the reduction in gamma synchrony and improvement in the PANSS general and total scores. However, this result did not persist after correction for multiple comparisons. The stability of absolute gamma synchrony despite significant clinical improvement implies that abnormal neuronal synchrony is a trait feature of psychosis. This supports the proposition that altered gamma synchrony may be an endophenotype for schizophrenia. Future research with a larger sample size is warranted to clarify these preliminary findings.