Corollary discharge and anomalous self-experiences in schizophrenia and bipolar disorder: A specificity analysis

[Display omitted] •Suppression of N1 event-related potential during speech was significantly reduced in schizophrenia patients.•Bipolar disorder patients exhibited intermediate sensory attenuation between the schizophrenia and control group.•The extent of N1 suppression inversely correlated with the severity of Anomalous Self-Experiences in schizophrenia, but not in bipolar disorder. The Corollary Discharge (CD) mechanism inhibits self-generated speech sound perception, appearing disrupted in schizophrenia and potentially contributing to Anomalous Self-Experiences (ASEs). However, it remains unclear if this alteration and its correlation with ASEs extend to other psychotic disorders. Electroencephalography was used to study the N1 Event-Related Potential (ERP) as an index of CD-mediated suppression in the auditory cortex across thirty-five participants with schizophrenia, twenty-six with bipolar disorder, and thirty healthy controls. Auditory N1 was elicited by two conditions: real-time listening to self-pronounced vowels while speaking through connected microphone and earphones (listen/talk −or talk condition in previous literature-) and passive listening to the same previously recorded self-uttered vowels (listen/no talk −or listen condition-). N1 ERP amplitude was lower in the listen/talk condition compared to listen/no talk across all groups. However, N1 suppression was significantly reduced in schizophrenia, with bipolar patients showing intermediate attenuation between both groups (i.e., non-significantly different from controls). Furthermore, N1 suppression inversely correlated with ASEs severity only in schizophrenia. Dysfunction of the CD mechanism may be a defining feature of schizophrenia, where it is connected to ASEs. These results corroborate previous findings linking auditory N1 ERP suppression with disrupted CD mechanism in schizophrenia, but not in bipolar disorder.