EEG microstates, acute phase negative symptoms of schizophrenia and antipsychotic treatment response

EEG microstates are transient scalp topographies reflecting whole-brain electric potential that remain quasi-stable for 60-120 ms. Microstates exhibitalterations across all phases of schizophrenia; especially an increased microstate C and a decreased microstate D were linked to aberrant salience. We aimed to investigate the relationship of microstates with illness severity in the positive, negative, disorganized, excited and depressed symptoms domains, and with response to antipsychotics. Forty-five inpatients were clinically evaluated at admission and 40 patients were also assessed after 6 weeks, to determine response to treatment; patients and 31 healthy controls underwent a 5-min resting-state EEG with 128-electrodes, to assess microstates A-E. The severity of negative symptoms was negatively associated with microstate C time coverage (trend = - 0.5249; P = 0.0078) and duration (trend = -0.737; P = 0.0001). In responders vs non-responders to treatment, microstate C had increased time coverage (p = 0.0052; d = -0.979), duration (P = 0.0168; d = -0.836) and global explained variance (GEV; P = 0.0046; d = -0.995), microstate D occurrence was reduced (P = 0.0044; d = -1.010), microstate E time coverage (p = 0.0148; d = 0.853), occurrence (P = 0.0037; d = 1.030) and GEV were reduced (P = 0.0115; d = 0.885). All the above reported findings remained significant when controlling for multiple comparisons.In conclusion, findings corroborate the hypothesis that the microstate CD imbalance is a key pathophysiology mechanism of schizophrenia, herein not only related to negative symptoms, but also predicting the response to antipsychotics, together with microstate E dynamics.