Functional network analysis of insight in resting-state brain activity

Insight occurs when problem solutions arise suddenly and is associated with an "Aha!" experience. While much research on insight has focused on event-related, goal-directed neural responses, there is growing interest in the spontaneous, resting-state brain activity. A recent study using high-density electroencephalograms (EEG) has demonstrated a dependence of task-related processing on the preceding resting state, but based on the power spectrum of individual electrodes in different frequency bands. In the current study, we sought to test the influence of resting-state functional networks on subsequent problem-solving strategy. We examined healthy subjects at rest who were subsequently directed to solve a series of anagrams to assess resting-state EEG network activity, as measured by coherence and Granger causality. Subjects were divided into two groups based on the proportion of anagram solutions derived with self-reported sudden insight versus analytic search. In this work, we mainly focused on gamma-band (30-40 Hz) activity, as it has been predominantly implicated in a wide variety of cognitive processes, and more importantly associated with insight solutions. Coherence analysis revealed that, within the gamma frequency band, there was a large-scale distributed resting-state network over the right hemisphere, with a network hub centering at the right anterior temporal lobe, for sudden insight relative to analytic search. Further analysis of the observed network with Granger causality indicated that there is a significant directional influence, originated from the network hub at the right anterior temporal lobe. These findings indicate that the spatial focus of the insight effect is at the right anterior temporal lobe, a result consistent with the hypothesis of right-lateralized hemispheric asymmetry.