From pre-stimulus preparation to the "Aha" burst: Unraveling the dynamics of perceptual insight with multi-method EEG.

How does the brain transform a confusing perceptual input into a sudden "Aha" experience? To investigate the neurocognitive dynamics of perceptual insight, we employed an embedded Chinese character task in which twenty-six eligible participants judged whether a source character contained a previously presented target. Targets were embedded either in a hidden/intersecting manner or in an unhidden/non-intersecting manner, allowing us to compare successful recognition under different restructuring demands. Matched invalid counterparts were also included as control conditions. Behaviorally, the hidden condition was associated with greater solution difficulty, followed by stronger "Aha" experiences-characterized by heightened surprise and suddenness-upon successful recognition. Electrophysiologically, relative to the unhidden condition, the hidden condition was associated with a more negative frontal N2 and a less positive parietal late positive component (LPC), consistent with differences in conflict-related and restructuring-related processing. Time-resolved multivariate pattern analysis (MVPA) further showed that neural activity reliably distinguished valid-hidden from valid-unhidden trials during a post-stimulus interval (430-480 msec). In addition, lower pre-source alpha power for hidden relative to unhidden trials predicted stronger hidden-relative-to-unhidden increases in Jolt and overall Aha scores. Together, our findings suggest that successful recognition of hidden targets is not merely more difficult perception, but is associated with a distinct phenomenological and neural profile. More broadly, perceptual insight appears to unfold dynamically, from pre-source neural-state differences to later stimulus-driven processing stages during successful recognition.