| 其他摘要 | Resting-state functional magnetic resonance imaging (fMRI) is valuable in basic and clinical psychology due to its unique benefits. However, there is a critical question that current research on resting-state fMRI has overlooked: does the data obtained from "resting-state" fMRI only come from the "resting"/"empty" brain? Endogenously driven self-generated thought/spontaneous thought is a complex and heterogeneous phenomenon prevalent in people's daily lives, particularly during periods without external cognitive demands, such as during resting-state scans. Recent research has started to investigate the effects of ongoing mental activity on brain activity during resting-state scans, but progress has needed to be faster. While self-generated thought research provides insights, most has focused on task contexts, with limited research on resting states. The classical empirical sampling (ES) approach has made significant strides in self-generated thought research. However, existing research paradigms restrict it, and the direct representation of self-generated thought in brain activity remains unclear. Moreover, the content of self-generated thought is diverse, closely linked to its complex effects, and strongly associated with mental disorders. However, methodological constraints limit the exploration of self-generated thought content characteristics to a few single dimensions, requiring new research methods to expand exploration. Therefore, this paper focused on these two interrelated issues and delved deeply into the characteristics and neural representations of self-generated thought in a resting state, which refers to a state of mind with no obvious external tasks or stimulation.
The paper focused on addressing limitations in methods used to investigate self-generated thought, and first explored the feasibility and effectiveness of using think-aloud as a more direct measure of resting-state self-generated thought. After establishing the feasibility of this method, the study integrated natural language processing (NLP) to quantitatively analyze the content of self-generated thought, calculating indicators of thought content divergence and expressions of sadness. Furthermore, the study investigated the relationship between these content features and individual traits, establishing that rumination is a sticky and negative form of self-generated thought. Overall, the study clarified the potential value of using the think-aloud method to investigate resting-state self-generated thought, as this method not only enables real-time data collection but also provides rich information about the content of self-generated thought, thereby facilitating research into the features of self-generated thought. Notably, researchers can achieve a more objective and quantitative analysis of thought content by combining the think-aloud method with NLP.
To address the issues of neglecting sustained mental activity during individual resting-state fMRI scans and unclear neural representation of self-generated thought, Study 2 employed the think-aloud method to resting-state fMRI scans (Think-Aloud fMRI) to clarify the impact of sustained thought flow on brain activity during resting一state fMRI scans and further defined the neural representation of self-generated thought. This study first explored the brain activation patterns under the Think-Aloud condition. Then, the study examined the relationship between the divergence of thought content and brain activation and found correlations across multiple brain regions. Finally, the study adopted an innovative approach that combines NLP with representation similarity analysis (RSA) and identified the neural representations of self-generated thoughts during rest at three different scales: voxel-level searchlight analysis, region-level analysis using the Schaefer 400-parcel, and systemic level of the Yeo seven networks. The results showed that self-generated thoughts during resting-state were associated with a broad range of brain regions spanning all seven Yeo networks. The proportion of significant brain regions, from largest to smallest, is the default mode network, frontoparietal control network, visual network, ventral attention network, somatomotor network, dorsal attention network, and limbic network. This study emphasizes the importance of considering sustained cognitive activity in resting一state fMRI and clarifies the spatial patterns of sustained thought flow during resting-state fMRI scans, providing support for spatiotemporal neuroscience and preliminary methodological support for Think-Aloud fMRI.
To further clarify the behavioral manifestations and their relationship with the brain activity of self-generated thought during the resting state with different content characteristics, based on the rich thinking content information provided by the think-aloud method, Study 3 explored the multidimensional content characteristics of self-generated thought during the resting state within and between groups from a behavioral perspective, furthermore, Study 4 used fMRI to investigate the corresponding brain activity patterns associated with different content characteristics of self-generated thought during resting-state, as described in detail below.
Study 3 conducted a multidimensional evaluation of the thought content features of the thought events collected through the think-aloud method. This evaluation included dimensions such as perceptual orientation (interoceptive, internal, and external) and social dimension (self, other). Besides, we evaluated the emotional experiences associated with self-generated thought using eight negative and four positive emotion dimensions. Based on this multidimensional analysis of thought content features, this study explored the thought content features of healthy individuals, healthy men and women, and individuals with depression during the resting state. Meanwhile, this study compared various thought content features between healthy men and women, and between those with depression and the healthy controls. The study found that self-generated thought during the resting state in individuals with depression exhibited unique characteristics, which differed significantly from those of healthy controls in several thought content dimensions.
Specifically, compared to healthy controls, self-generated thought in individuals with depression had less external focus, was more self-focused, less future-oriented, less attentive to positive events, more attentive to negative events, and exhibited lower levels of reflective thinking and higher levels of ruminative thinking. In terms of emotional experiences accompanying self-generated thought during the resting state, depression was associated with significantly higher levels of negative emotions, as evidenced by significantly higher levels of all eight negative emotions, and significantly lower levels of all four positive emotions, compared to healthy controls. Additionally, the study found significant differences in self-generated thought during the resting state between healthy men and women. Moreover, women exhibited similarities with individuals with depression in some thought content dimensions. Specifically, women exhibited higher levels of self-focus, greater attention to negative events, and higher levels of several negative emotions compared to healthy men. Finally, this study utilized NLP to develop regression models for multiple content assessments and a classifier for distinguishing between depression and healthy individuals. The findings validated the value and potential of the think-aloud method for clinical applications in MDD.
Based on Think-Aloud fMRI data and behavioral data of thought content characteristics, Study 4 used two analytical approaches to reflect the relationship between self-generated thought content characteristics and brain activity from different aspects: (1) the comparison analysis of each thought content characteristic and its baseline; (2) the correlation analysis between changes in thought content characteristics and changes in brain activity. Both analyses indicated a close connection between the content characteristics of self-generated thought and brain activity, and different thought content characteristics corresponded to different brain representations. In terms of the emotional experiences accompanying self-generated thought during the resting state, the study found that the overlapping and differential brain activity corresponding to different emotional experiences were detectable by the BOLD signal, and the neural representation of internally driven thought and externally induced emotions showed consistency. This study further emphasizes the significant impact of ongoing psychological activities during the resting state on brain activity and highlights the importance of studying self-generated thought content characteristics in more detail from a neural perspective, providing insights into the neural representation of self-generated thought content characteristics.
In summary, this paper focuses on the self-generated thought flow during resting一state and strives to advance research in this field, hoping to provide insights for resting-state fMRI research and self-generated thought domain. Given the limitations of current methods in the field, we first developed a method to directly measure self-generated thought during the resting state (Study 1). Subsequently, this method was applied in fMRI with NLP to clarify the representation of resting一state thought flow in large-scale brain networks using RSA (Study 2). Then, we systematically explored the behavioral performance of multidimensional content characteristics of self-generated thought within and between groups (Study 3) and investigated the corresponding brain activity patterns of different content characteristics of self-generated thought (Study 4). In short, this paper emphasizes the importance of investigating sustained thought flow during the resting state from multiple perspectives, revealing some content characteristics of self-generated thought during the resting state and obtaining a spatial map of brain activity corresponding to self-generated thought during the resting state. The theoretical and methodological support provided by this paper will help clarify the spatial structural characteristics of spontaneous brain activity and advance research in resting一state fMRI and self-generated thought domains. |
修改评论