S138. A PRELIMINARY STUDY ON ILLNESS INSIGHT MEASURED BY THE RELATIONSHIP BETWEEN ERN PATTERNS AND MMPI RESULTS IN PATIENTS WITH SCHIZOPHRENIA

BACKGROUND: The error-related negativity (ERN) is an event-related brain potential waveform peaking about 50 ms after error commission in choice-response tasks and may indicate a conflict between neural representations of correct and incorrect responses as stimulus processing continues after an error. Most previous studies consistently reported a reduced event-related potential (ERP) amplitude in patients with schizophrenia compared with normal controls. Some self-report measures derived from the Minnesota Multiphasic Personality Inventory (MMPI) are known to be associated with clinical observations in carefully diagnosed schizophrenia patients. In the MMPI, an elevation of the validity scales in the MMPI best distinguishes patients with schizophrenia from patients feigning schizophrenia, and the MMPI validity scales are known to provide a good reflection of illness insight in schizophrenia. Both the amplitudes of the Pe of the ERN and the scores of the MMPI validity scales are supposed to reflect, directly or indirectly, the illness insight of patients with schizophrenia. When the abovementioned results obtained in studies on the ERN or MMPI in patients with schizophrenia are taken together, we may presume that a certain relationship exists between the results of the ERN and the MMPI validity scales in terms of illness insight. Interestingly, as far as we know, there are no published studies that looked at the results of the ERN and the MMPI at the same time. We tried to perform an integrative examination of the relationship between the results of the ERN and MMPI tests in patients with schizophrenia as a method of measuring illness insight in patients with schizophrenia. METHODS: We reviewed the medical records of who were diagnosed as having schizophrenia based on the DSM-5. The protocol for the general ERP and ERN are as follows. 64 channels with M1 and M2 as reference electrodes Impedance: < 1 kΩ ERN: 1000 ms ERPs were recorded while the patients were performing the Stroop test. Independently of the ERP recording, the patients received an MMPI test. The relationship between the latency and amplitude of the ERN and the demographic and clinical variables was analyzed by a t-test, and correlation analyses were used for categorical and continuous variables. The statistical significance was set at p < 0.05. RESULTS: Of the total 18 patients (8 men and 10 women; age = 41.6 ± 15.8) whose data were reviewed, 5 were excluded due to poor understanding of the ERN instructions. Table 1. Demographic and clinical information of participated patients with schizophrenia Table 2. Partial correlation coefficients on variables after controlling for age and gender. DISCUSSION: The results for the association of ERN amplitude and latency with the MMPI validity scales showed that latency measures were positively associated with the MMPI validity scales that were related to the assessment of the overestimation of responses. Individuals who tended to exaggerate problems through over-responses showed increased ERN amplitude but decreased ERN Pe amplitude. Although caution is needed to interpret the results of this study due to limitations, our results suggest that ERP measurement could act as a biological marker for endophenotype in schizophrenia. Furthermore, ERP measurement might be used to visualize or to make concrete illness insight, which by its nature is difficult to measure objectively. REFERENCES: Yeung N, Botvinick MM, Cohen JD. The neural basis of error detection: conflict monitoring and the error-related negativity. Psychol Rev. 2004 Oct;111(4):931–959. Kansal V, Patriciu I, Kiang M. Illness insight and neurophysiological error-processing deficits in schizophrenia. Schizophr Res. 2014 Jun;156(1):122–7.