Abstract

Objectives: To compare the resting-state connectivity between ultra-high risk (UHR) subjects and controls (CNT) using the EEG microstate technique. Background: The brain is continuously active, even under conditions that no particular activity is being performed, to prepare the central nervous system for the arrival of new internal or external stimuli. Previously, resting-state brain connectivity abnormalities have been reported in schizophrenia (SZ) through the EEG microstate resting-state technique (which comprises four canonical A-phonological, B-visual, C-salience and D- attentional networks), however, little is known about this topic in early stages of the disease as the UHR syndrome. Materials and Methods: An EEG was performed in 20 UHR subjects and 27 CNT under resting conditions, considering 2 minutes of eyes-open and 2 minutes of eyes-closed recording. Then, we pre-processed the records and performed the EEG microstate analysis in an open source EEGLab toolbox for MATLAB. Finally, an unpaired t-test was performed to evaluate the differences of each microstate statistic (duration, coverage, occurrence, GEV and GFP) between both groups. Results and Conclusions: UHR subjects presented lower microstate D and higher microstate B coverage (%) compared to CNT, suggesting an abnormal resting-state connectivity in attentional and visual areas which are consistent with previous alterations seen in SZ and the 22q11 syndrome. No other EEG microstate statistics were found to be different between groups. These findings could represent a SZ trait marker with potential clinical utility due to its simple registration and analysis.