Resting state hyperconnectivity of the default mode network in schizophrenia and clinical high-risk state for psychosis.

Disrupted functional connectivity (FC) of the default mode network (DMN) may have a pathophysiological role in schizophrenia. However, functional magnetic resonance imaging (fMRI) of the DMN in schizophrenia patients has shown inconsistent results. It also remains unclear whether individuals with at-risk mental state (ARMS) have an altered DMN connectivity and whether it is related to clinical characteristics. This fMRI study examined resting-state FCs of the DMN and its relevance to clinical/cognitive variables in 41 schizophrenia patients, 31 ARMS individuals, and 65 healthy controls. Compared with controls, schizophrenia patients had significantly increased FCs within the DMN and between the DMN and diverse cortical areas, whereas ARMS patients had increased FCs only between the DMN and occipital cortex. FC of the lateral parietal cortex with superior temporal gyrus was positively correlated with negative symptoms in schizophrenia, whereas FC of that with interparietal sulcus was negatively correlated with general cognitive impairment in ARMS. Our findings suggest that increased FCs between the DMN and visual network commonly seen in schizophrenia and ARMS subjects may reflect a network-level disturbance representing a general vulnerability to psychosis. In addition, FC changes related to the lateral parietal cortex may underpin clinical characteristics of ARMS and schizophrenia subjects.

Features of Duration Mismatch Negativity Around the Onset of Overt Psychotic Disorders: A Longitudinal Study.

Reduced amplitude of duration mismatch negativity (dMMN) has been reported in psychotic disorders and at-risk mental state (ARMS); however, few longitudinal MMN studies have examined the amplitude changes during the course of psychosis. We compared dMMN amplitude between ARMS individuals with later psychosis onset and those without, and we longitudinally examined potential dMMN changes around psychosis onset. Thirty-nine ARMS subjects and 22 healthy controls participated in this study. Of the 39 ARMS subjects, 11 transitioned to psychosis (at-risk mental state with later psychosis onset [ARMS-P]) during follow-up and 28 did not (at-risk mental state without later psychosis onset [ARMS-NP]). dMMN was measured twice using an auditory oddball paradigm with a mean interval of 2 years. Follow-up dMMN data were available for all but four ARMS-P subjects. dMMN amplitude at baseline was smaller in ARMS-P subjects compared with control and ARMS-NP subjects. Additionally, ARMS-P subjects displayed a longitudinal decline in dMMN amplitude, which was not present in control and ARMS-P subjects. We also observed a progressive decline in dMMN amplitude during the transition period, suggesting dynamic brain changes associated with the psychosis onset. Our findings implicate dMMN amplitude as a biological predictor of future psychosis onset in high-risk individuals, which may be used for early detection and intervention of psychosis.