398. Disrupted occipital-parietal alpha oscillations in first-episode psychosis

Abstract

Abstract Background First-episode psychosis(FEP) marks a critical stage in the early course of schizophrenia-spectrum disorders, during which neurophysiological abnormalities may be most pronounced and minimally influenced by chronicity or long-term medication exposure. Early identification of oscillatory biomarkers is essential because disruptions in cortical synchronization during this period are strongly linked to later cognitive decline and functional impairment. Prior EEG and MEG studies have reported abnormalities in various oscillatory bands(theta, alpha, beta, gamma) and across different cortical regions, leading to differences across studies. This variability highlights the need for comprehensive, spectrum-wide analyses and the use of open, reproducible datasets to clarify early neural signatures of psychosis. Aims & Objectives This study aimed to characterize resting-state oscillatory abnormalities in FEP by analyzing publicly available EEG data from OpenNeuro, examining all 60 scalp sensors and the entire 1-40 Hz frequency range to detect frequency- and region-specific disruptions without prior assumptions. Method Resting-state EEG recordings were obtained from 48 individuals with schizophrenia-spectrum psychosis and 24 healthy controls. Participants completed a 5-minute eyes-open resting condition. Preprocessing was performed in EEGLAB, including 1-40 Hz bandpass filtering, artifact rejection, and independent Component Analysis to remove ocular and muscular artifacts. Oscillatory power was computed for each electrode across the full 1-40 Hz range. Group differences were evaluated using cluster-based permutation testing in FieldTrip, with 1,000 permutations and a cluster-forming threshold of p < .05, enabling spatially and spectrally coherent inference while controlling for multiple comparisons. Results A significant negative cluster emerged within the 7-10 Hz frequency range, predominantly involving occipital and left parietal regions. Individuals with FEP exhibited significantly reduced alpha-band oscillatory power in this cluster compared with healthy controls. No additional clusters reached significance across other frequencies in the 1-40 Hz spectrum. Discussion & Conclusions The observed posterior alpha reduction aligns with evidence linking sensory integration deficits and impaired thalamo-cortical modulation to the earliest stages of schizophrenia. Importantly, these abnormalities were detected during a simple resting-state condition, underscoring their promise as early neurophysiological markers rather than consequences of chronic illness. Because early cortical dysregulation is strongly associated with long-term clinical outcomes, the present findings highlight resting-state EEG as a scalable tool for identifying neural dysfunction at illness onset. The use of open-access datasets such as OpenNeuro enhances reproducibility and supports future longitudinal research to determine whether posterior alpha attenuation predicts symptom progression, treatment response, or enduring functional impairment.