| 其他摘要 | In daily life, people often experience mind wandering. Mind wandering is a state of consciousness in which individual's attention is disengaged from the present task to internal information unrelated to the task, such as personal goals, fantasies or other thoughts, and away from the present moment. So far, studies have found that mind wandering is more frequent in patient with schizophrenia than in healthy controls and is associated with clinical symptoms, therefore, studying mind wandering in schizophrenia may be helpful to understand its psychopathology. Individuals with schizotypal traits are at risk for schizophrenia, they are free of hospitalization and medication and can be also helpful to the study of schizophrenia. However, there are few studies on mind wandering in individuals with schizotypal traits.
In recent years, scholars have widely applied EEG technology to the research of mind wandering to investigate the neural mechanism of mind wandering and have achieved important findings. However, the neural mechanism of mind wandering in individuals with high schizotypal traits remains to be explored. In addition, most previous studies were conducted in laboratory settings or measured using questionnaires which had low ecological validity. Therefore, it is necessary to further explore the differences of mind wandering in daily life manifestations between individuals with high and low schizotypal traits.
The present thesis aimed to investigate the neural mechanism of mind wandering in individuals with schizotypal traits with both resting state EEG and task-based EEG, and to explore mind wandering in daily life in individuals with schizotypal traits via experience sampling method. Three studies were included.
In Study 1，the neural mechanism of mind wandering in individuals with schizotypal traits was explored using resting state EEG. A total of 48 individuals with high schizotypal traits individuals and 50 individuals with low schizotypal traits completed the Mind Wandering Questionnaire and had their resting state EEG recorded.
The main EEG index analyzed was the theta beta power ratio (TBR). Previous studies showed that TBR was related to attention control and mind wandering. The results showed that the high schizotypal group had more frequent mind wandering than the low schizotypal group. In the high schizotypal group, frontal region TBR was significantly negatively correlated with mind wandering score, while no significant correlation was found in the low schizotypal group, suggesting that the neural mechanism of mind wandering may be different between the two groups.
In Study 2, task-based EEG (i.e., event-related potential, ERP) was used to explore the neural mechanism of mind wandering in individuals with high schizotypal traits. A total of 35 individuals with high schizotypal traits and 32 individuals with low schizotypal traits completed the sustained attention to response task (SART) with EEG recorded, thought probes were presented occasionally to inquire the attention status of participants. According to the responses (focus on task or mind wandering), the neural mechanism related to mind wandering was analyzed by comparing mind wandering with focus on task. At the same time, the participants also completed the Mind Wandering Questionnaire, Spontaneous Mind Wandering Questionnaire and Intentional Mind Wandering Questionnaire. Results showed that mind wandering score, intentional mind wandering and unintentional mind wandering score were significantly higher in the high schizotypal group than the low schizotypal group. There was no significant group difference in the rates of mind wandering reported in the SART task. However, there were group differences in the amplitude of components associated with mind wandering, the frontal P2 amplitude in the high schizotypal group was smaller than that in the low schizotypal group, the frontal N2 amplitude in the high schizotypal group was larger than that in the low schizotypal group, and the frontal P3 amplitude in the high schizotypal group was smaller during mind wandering than focus on task, but there was no such significant difference in the low schizotypal group. These results suggest that the group difference in the neural mechanism of mind wandering may involve sensory processing and cognitive control.
In Study 3, the manifestations of mind wandering in daily life in individuals with schizotypal traits were examined via experience sampling. A total of 28 individuals with high schizotypal traits and 31 individuals with low schizotypal traits completed an experience sampling task. The participants were required to click the questionnaire link received by Samply Research to fill in the questionnaire within 8 days, and eight questionnaires were received each day. The questions were about attention status (mind wandering or focus on task), characteristics of mind wandering, emotional status, and ongoing tasks, etc. Results showed that there was no significant difference between the two groups in the overall proportion of mind wandering, both groups reported mind wandering on about 30% of occasions. The high schizotypal group had a higher frequency of mind wandering related to personal goals and directed to the future; thought status was predicted by degree of freely-moving and controllability in the high schizotypal group to a higher degree than the low schizotypal group, and thought status was predicted by the degree of interested in ongoing events in the low schizotypal group to a higher degree than the high schizotypal group. In the low schizotypal group, mind wandering at timepoint t+1 was predicted by emotional valance at timepoint t, while in the high schizotypal group, there was no such relationship. These results suggest that the high schizotypal group and the low schizotypal group had different manifestations of mind wandering in daily life.
To conclude, the present thesis systematically explored the neural mechanism and daily manifestations of mind wandering in individuals with schizotypal traits, results indicated that the correlation patterns of resting state EEG and mind wandering between the two groups may be different, the group difference of neural mechanisms related to mind wandering may involve sensory and perceptual processing and cognitive control. Though the overall frequency of mind wandering in daily life was similar between groups, there were some differences in the content and relationship to emotion between groups. The present thesis is helpful for understanding the differences in daily life manifestations and neural mechanism of mind wandering in individuals with schizotypal traits, and provides possible neurophysiological indicators, so as to more comprehensively understand the complex relationship between mind wandering and the brain in schizophrenia spectrum, and provide theoretical basis for early identification and intervention. |
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