Psychopathology was assessed in patients with SLPE using the Brief Psychiatric Rating Scale (BPRS) on the day of the EEG recordings. A 4-factor structure of clinical symptoms, reported to fit the data better than the typical 5-factor BPRS model for schizophrenia, was used for analyses [42]. Symptoms are grouped into four major syndromes: ‘thought disturbance’ (positive symptoms), ‘anergia’ (negative symptoms), ‘disorganization’ and ‘affect’ domain. Positive symptoms are determined by summing up scores on grandiosity, suspiciousness, hallucinatory behavior and delusion/unusual-thought content items. Negative symptoms include emotional withdrawal, motor retardation, uncooperativeness and blunted affect, while disorganization was defined by conceptual disorganization, tension and mannerisms/posturing, and the affect domain by somatic concern, anxiety, guilt feelings, depressed mood, and hostility. Since hallucinations and delusions are the core psychiatric symptoms of schizophrenia-like disorders, we also used the raw scores of 1) hallucinatory behavior and 2) unusual-thought content (delusions) items of the BPRS scale for analyses of the data.
