The neural basis of insight problem solving: an event-related potential study.

The electrophysiological correlates of successful insight problem solving (Chinese logogriphs) were studied in 18 healthy subjects using high-density event-related potentials (ERPs). A new experimental paradigm (learning-testing model) was adopted in order to make subjects find a solution on their own initiative rather than receive an answer passively. Results showed that Successful guessed logogriphs elicited a more positive ERP deflection (P200-600) than did Unsuccessful guessed logogriphs in the time window from 200 to 600 ms after onset of the stimuli. Subsequently Successful logogriphs elicited a more negative ERP deflection than did Unsuccessful logogriphs in the time windows of 1500-2000 ms (N1500-2000) and 2000-2500 ms (N2000-2500). Maps of the P200-600 showed strong activity in the midline parieto-occipital scalp regions. Dipole analysis localized the generator of P200-600 in the left superior temporal gyrus and parietotemporo-occipital cortex areas. The N1500-2000 and N2000-2500 had a distinct activation over left frontal scalp regions. Dipole analysis localized the generator of the N1500-2000 in the anterior cingulate cortex (ACC) and the N2000-2500 in the posterior cingulate cortex (PCC). This result indicates that the parietotemporo-occipital cortex areas might be involved in forming rich associations in the early stage of successful logogriph solving. Then, the ACC might play an important role in the breaking mental set and the forming of novel associations. At last, "Aha" feeling might activate the PCC.