Chunk decomposition plays an important role in cognitive flexibility in particular with regards to representational change, which is critical for insight problem solving and creative thinking. In this study, we investigated the cognitive mechanism of decomposing Chinese character chunks through a parametric fMRI design. Our results from this parametric manipulation revealed widely distributed activations in frontal, parietal, and occipital cortex and negative activations in parietal and visual areas in response to chunk tightness during decomposition. To mentally manipulate the element of a given old chunk, superior parietal lobe appears to support element restructuring in a goal-directed way, whereas the negatively activated inferior parietal lobe may support preventing irrelevant objects from being attended. Moreover, determining alternative ways of restructuring requires a constellation of frontal areas in the cognitive control network, such as the right lateral prefrontal cortex in inhibiting the predominant chunk representations, the presupplementary motor area in initiating a transition of mental task set, and the inferior frontal junction in establishing task sets. In conclusion, this suggests that chunk decomposition reflects mental transformation of problem representation from an inappropriate state to a new one alongside with an evaluation of novel and insightful solutions by the caudate in the dorsal striatum.

Generalized anxiety disorder (GAD) is one of the most common anxiety disorders. The brain’s dysfunctional processing of interoceptive information is increasingly recognized as an important component of anxiety disorders. However, the neural mechanisms remain insufficiently understood. In the present study, patients with GAD and healthy control participants underwent an eyes-closed (EC) resting state (interoception) and eyes-open (EO) resting state (exteroception) without paying conscious attention to heartbeat. Electrocardiography (ECG) and electroencephalography (EEG) signals were recorded at the same time. The results show that in healthy controls, the heartbeat-evoked brain potential (HEP) was modulated by the conditions, with a significantly higher amplitude under EC than EO, while this was not the case in GAD patients. Further analysis revealed that the dysfunction of HEP modulation in GAD patients may be attributed to excessive interoceptive processing under EO, with a marginally higher HEP in GAD than in the healthy controls. Finally, the right prefrontal HEP amplitude during EC condition was significantly correlated with the severity of the patients’ anxiety symptoms. Our results suggest that altered cortical processing of interoceptive signals may play an important role in the pathophysiology of generalized anxiety disorder.

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