Cathodal Stimulation on Left Dorsolateral Prefrontal Cortex Facilitates Restructuring Process Underlying Insight Problem Solving

Studies have shown that weakened executive control by cathodal stimulation targeting the prefrontal cortex (PFC) improves performance on classical insight problem solving. However, it remains unclear how cathodal stimulation on PFC impacts the restructuring processes underlying insight problem solving, and how task-specific cognitive demands influence the PFC neuromodulation effects. Here, we employed a multimodal approach integrating eye-tracking with high-definition transcranial direct current stimulation (HD-tDCS) to detect the restructuring process of two types of matchstick problems which involved different cognitive demands, constraint relaxation, and chunk decomposition. Results showed that cathodal stimulation of left dorsolateral PFC has differential effects on both the task performance and the restructuring process of two types of problems. The stimulation effects allowed solvers to notice the crucial elements of the constraint relaxation problem and improved solution rate, while that made solvers gaze more on empty portions of the chunk decomposition problem but without better performance. This finding suggests that disrupting the natural functioning of PFC plays a causal role in the restructuring processes underlying insight problem solving, with its effects operating contingent on task-specific cognitive demands. This study provides novel methodological insights into the intricate cognitive dynamics underlying neuromodulation-mediated problem-solving processes.