Electrophysiological evidence for the characteristics of implicit self-schema and other-schema in patients with major depressive disorder: An event-related potential study

BACKGROUND: The significance of implicit self-schema and other-schema in major depressive disorder (MDD) is highlighted by both cognitive theory and attachment theory. The purpose of the current study was to investigate the behavioral and event-related potential (ERP) characteristics of implicit schemas in MDD patients. METHODS: The current study recruited 40 patients with MDD and 33 healthy controls (HCs). The participants were screened for mental disorders using the Mini-International Neuropsychiatric Interview. Hamilton Depression Rating Scale-17 and Hamilton Anxiety Rating Scale-14 were employed to assess the clinical symptoms. Extrinsic Affective Simon Task (EAST) was conducted to measure the characteristics of implicit schemas. Meanwhile, reaction time and electroencephalogram data were recorded. RESULTS: Behavioral indexes showed that HCs responded faster to positive self and positive others than negative self (t = −3.304, p = 0.002, Cohen’s d = 0.575) and negative others (t = −3.155, p = 0.003, Cohen’s d = 0.549), respectively. However, MDD did not show this pattern (p > 0.05). The difference in other-EAST effect between HCs and MDD was significant (t = 2.937, p = 0.004, Cohen’s d = 0.691). The ERP indicators of self-schema showed that under the condition of positive self, the mean amplitude of LPP in MDD was significantly smaller than that in HCs (t = −2.180, p = 0.034, Cohen’s d = 0.902). The ERP indexes of other-schema showed that HCs had a larger absolute value of N200 peak amplitude for negative others (t = 2.950, p = 0.005, Cohen’s d = 0.584) and a larger P300 peak amplitude for positive others (t = 2.185, p = 0.033, Cohen’s d = 0.433). The above patterns were not shown in MDD (p > 0.05). The comparison between groups found that under the condition of negative others, the absolute value of N200 peak amplitude in HCs was larger than that in MDD (t = 2.833, p = 0.006, Cohen’s d = 1.404); under the condition of positive others, the P300 peak amplitude (t = −2.906, p = 0.005, Cohen’s d = 1.602) and LPP amplitude (t = −2.367, p = 0.022, Cohen’s d = 1.100) in MDD were smaller than that in HCs. CONCLUSION: Patients with MDD lack positive self-schema and positive other-schema. Implicit other-schema might be related to abnormalities in both the early automatic processing stage and the late elaborate processing stage, while the implicit self-schema might be related only to the abnormality in the late elaborate processing stage.