This project will compare gamma synchrony in 55 subjects with recent onset psychosis and 110 age-, sex- and education-matched controls. An auditory oddball and a visual working memory paradigms were used, to explore the hypothesis that disturbed ‘binding’ in psychosis is not limited to auditory processing.
The EEG data were analyzed using a measure of phase synchrony, described in detail elsewhere (Haig et al. 2000). There were two important differences in the present work. First, multiple frequencies were assessed, rather than simply 40 Hz. Second, a 512-ms fast Fourier transform window was used to estimate the phases at a given frequency, rather than 256 ms. This provided an improved frequency resolution (∼2 Hz), at the expense of temporal resolution. The phase synchrony was estimated for six frequency bands between 35 and 45 Hz at 10-ms intervals.
Multiple analyses of covariance (controlling for age) showed significant excesses of gamma synchrony in the psychosis group for both paradigms with different topographical distribution in each. In general, there were more marked differences in the auditory paradigm, a dominant frontal and left-sided abnormality in both, with elevated synchrony posteriorly in the visual paradigm.
Elevated synchrony in both paradigms supports the potential role of abnormal assembly formation as a generalized mechanism responsible for the production of psychotic symptoms.