Identifying The Core Neural Substrates Of Procrastination

Defined as “to voluntarily delay an intended course of action despite expecting to be worse off for the delay”, procrastination has become a prevalent problematic behavior that brings serious consequences to individuals who suffer from it. Previous studies have proposed several models and theories to interpret this phenomenon, such as the temporal motivation theory and the conceptual model. According to these accounts, procrastination could be attributed to several factors assigned to cognitive and affective prospects. However, to date, the dominant factors contributing to procrastination remain unclear. In recent years, the development of functional magnetic resonance imaging(fMRI) has provided new perspectives in exploring the core mechanisms of mental processes. Nevertheless, no study has ever examined the neural substrates related to procrastination. Therefore, the present study aimed to explore the neural substrates subserving procrastination to give a better interpretation about the mental mechanisms of procrastination.In study 1, we utilized resting-state fMRI(RS-fMRI) to unravel the regional activity and neural networks underlying procrastination with the employment of regional homogeneity(ReHo), amplitude of low frequency fluctuation(ALFF) and functional connectivity(FC). The results were as follows: 1) the behavioral procrastination was positively correlated with the zReHo values in the parahippocampal cortex(PHC) and the ventromedial prefrontal cortex(vmPFC), while negatively correlated with the zReHo values in the anterior prefrontal cortex(aPFC) and the posterior cingulate cortex(PCC); 2) the zALFF results showed that the PHC and the vmPFC were positively correlated with procrastination, however, only the aPFC showed a negative correlation with procrastination; 3) the functional connectivity between the aPFC and the anterior medial prefrontal cortex, and between the aPFC and the PCC positively predicted procrastination; while the connectivity between the vmPFC and several other regions, including the dorsomedial prefrontal cortex, the superior frontal cortex, the bilateral inferior prefrontal cortex and the middle temporal cortex was negatively correlated to procrastination. These findings suggested that the aPFC, the PHC and the vmPFC are core regions subserving procrastination. And the behavioral procrastination could be attributed to the overwhelming effect of the medial temporal cortex system activity on the prefrontal cortex responsible for cognitive control, and to the failure of the aPFC inhibition on the default mode network(DMN).To further clarify the core mechanisms of procrastination, study 2 focused on revealing the common neural substrates shared by procrastination, impulsivity and self-control. This idea is grounded on the evidence that procrastination, impulsivity and self-control show high correlations with each other, suggesting a shared mental process within them. In study 2, we employed RS-fMRI with structural equation model analysis. We found that: 1) procrastination was negatively correlated with the regional activity of the aPFC, and the connectivity between the aPFC and several regions, such as the PCC, the PHC and the thalamus could positively predicted procrastination; 2) behavioral impulsivity was positively correlated with the regional activity of the vmPFC; 3) the regional activity of the aPFC showed a positive correlation with self-control and in addition, the connectivity between the aPFC and several other regions, including the thalamus, the PHC, the posterior insula, the bilateral PCC and the bilateral parietal cortex was negatively correlated with behavioral self-control; 4) the structural equation model showed that the procrastination, impulsivity and self-control shared a common mental process, which was subserved by the regional activity of the aPFC and the vmPFC, as well as the functional connectivity between the aPFC and several regional pertaining to the default mode network and the limbic system. Our results suggest that a temporal-based self-control component could be a common process shared by procrastination, impulsivity and self-control. Furthermore, the process of the procrastination, impulsivity and self-control is determined by the top-down cognitive control exerted by the aPFC on the DMN and the limbic system. Therefore, the present study verified the findings of study 1, and unraveled the core component of procrastination and the subserving neural substrates.Combined study 1 and study 2, the present findings indicate that procrastination in nature results from the failure of self-control. The aPFC is the core neural substrate of procrastination, which functions to initiate executive control by integrating cognitive and affective information. And this executive control is achieved by inhibiting the neural activity of the DMN and the limbic system. Procrastination occurs once the hyperactivity of the DMN and the limbic system overrides the top-down control process of the aPFC. Therefore, the present study reveals the core neural bases underpinning procrastination and provide the intervention targets for treatment.