Chunk decomposition (CD) is a specific type of insight that contains the process of breaking up perceptual patterns or chunks into elements so that they can be reorganized in a different manner. Although the cognitive processes of CD were demonstrated by the matchstick arithmetic tasks using Roman number (Knoblich et al., 1999), its brain basis was still unclear. In this project, we explore the cognitive brain mechanism of CD by using Chinese characters as materials. Chinese characters are composed of radicals, which in turn are composed of strokes. So we were able to manipulate the tightness of the chunk by defining the radical- or stroke-level CD. Combined ERPs and fMRI experiments revealed several interesting principles of CD. Most importantly, the results demonstrated that there were multiple difficulties (i.e., chunk familiarity and chunk tightness) underlying CD. Different difficulties involed different neural network and had different effects on CD. Dynamic causal modeling (DCM) also revealed that chunk familiarity and perceptual tightness made a combined contribution to highlight not only the "what" and the "where" streams, but also the effective connectivity from the left inferior temporal gyrus to the left superior parietal lobule.
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