tACS for Self-Other Boundary in Schizophrenia

This clinical trial investigates whether a non-invasive brain stimulation technique called transcranial alternating current stimulation (tACS) can improve the ability to distinguish between "self" and "others" in patients with schizophrenia. The intervention targets the medial prefrontal cortex (mPFC), a brain region critical for self-awareness, using 10Hz stimulation at 2mA for 20 minutes daily over five consecutive days.

The study has two main objectives. First, it aims to characterize the underlying mechanisms of self-other boundary dysfunction in schizophrenia by comparing behavioral and brain activity patterns among three participant groups: patients with schizophrenia, individuals with high schizotypal traits, and healthy volunteers. During this mechanism phase, participants perform two computer-based self-other face recognition tasks designed to manipulate prior probability (varying the proportion of self vs. other faces across blocks) and perceptual uncertainty (adjusting the Gaussian blur level of face images), while their brain activity is recorded via EEG. Behavioral performance (response time, accuracy, and sensitivity d') and EEG markers (alpha-band power, N170, and P1 components) are analyzed to quantify deficits in predictive coding.

Second, the study aims to evaluate the therapeutic efficacy of tACS in a randomized, double-blind, sham-controlled trial. The primary hypothesis is that active tACS, compared to sham stimulation, will significantly improve patients' accuracy in distinguishing self from other faces, accompanied by enhanced alpha-band brain oscillations and reduced scores on the Examination of Anomalous Self-Experience (EASE) scale.

All participants will undergo clinical assessments, complete the face recognition tasks while their brain activity is monitored via EEG, and complete follow-up assessments 48 hours after the last stimulation session. The findings from this study may provide a novel, mechanism-based non-pharmacological intervention for addressing core self-disturbance in schizophrenia, potentially improving patients' social functioning and quality of life.