Neuropsychological Study Of Theory Of Mind In Schizophrenia

Objective Successful social intercourse rests on having a Theory of Mind (ToM), an understanding of how others'behaviors can be understood in terms of internal mental states, such as beliefs, desires, intentions, and emotions. The ToM skills are the most important mediator for social functioning. Previous literatures of cognitive neuroscience have conceptualized ToM as comprising two components: the social-perceptual component and social-cognitive component. Numerous studies have demonstrated that the ToM ability was impaired in schizophrenia. However, there is no research to ask whether the both two ToM components are damaged in schizophrenia. We began this study with the proposal to investigate the ToM ability in schizophrenia on a componential view. Cognitive neuropsychiatric researches are interested in the internal laws between the cognitive disabilities and the psychotic symptoms. The internal association between the ToM deficits in schizophrenia and psychotic symptoms has been widely investigated. Nevertheless, the inconsistent results were received. Clinically, the depressed patients were familiar with psychotic symptoms. We aimed to ask whether the psychotic symptoms are related with ToM ability in depression by comparing the ToM performances between the psychotic depressed patients and nonpsychotic depressed ones. The method of event-related potentials (ERP) is widely conducted in psychological studies, which are termed as"the psychological windows". Thus, we also investigated the temporal-spatial characteristics of social-perceptual processing in schizophrenia by an ERP experiment.Method 52 schizophrenic patients, 56 depressed patients (23 psychotic depressed patients, 33 nonpsychotic depressed patients), and 53 normal controls completed the Eyes Task, Faux pas Task, Verbal Fluency Test (VFT), and Digit Span Test (DST). The schizophrenic patients also completed Positive And Negative Syndrome Scale (PANSS) assessing psychotic symptoms. All depressed patients also completed Beck Depression Inventory (BDI-II) and Brief Psychiatric Rating Scale (BPRS) assessing clinical symptoms. In the ERP study, 15 schizophrenic patients and 15 normal controls were investigated by an Eyes Task for ERP.Results The schizophrenic patients and depressed patients were significantly impaired in their ability on social-perceptual component in Eyes Task compared to normal controls. Also, the schizophrenic patients and depressed patients were significantly impaired in their ability on social-cognitive component in Faux pas Task. The schizophrenic individuals and depressed ones performed significantly worse than normal controls on VFT. No significant difference was found on Gender Recognition in Eyes Task, Control Questions in Faux pas Task, and DST among groups. The psychotic depressed patients significantly performed worse than nonpsychotic depressed individuals on tasks involving ToM (i.e. Mind Reading and Faux pas Questions), when the BDI-II scores were controlled. In schizophrenic group, a negative significant association was found between the performances of Mind Reading and negative symptoms scores. Also, a positive significant association was found between the performances of Mind Reading and VFT. In depressed group, the negative significant associations were found between the ToM performances and BPRS total scores or hostile-suspiciousness factor,when the BDI-II scores were controlled.In normal controls, N2 amplitude showed a significant main effect of task due to Mind Reading amplitude larger than Gender Recognition. Also, N2 amplitude showed a significant interactive effect of task and location in normal controls. The Mind Reading amplitude was lager than Gender Recognition on F4, and T4. Significant differences were found between the schizophrenic patients and normal controls on N2 amplitude of F4 and T4.Conclusion Both the ToM social-conceptual component and the ToM social-cognitive components were impaired in schizophrenia and depression. There may be some inherent laws between the psychotic symptoms and ToM deficits. The ToM social-perceptual processing may be related with N2 component in right fronto-temporal regions. ToM social-perceptual component disability may associate with the abnormal neuroelectrophysiological activity in right fronto-temporal regions.