Neural correlates of the 'Aha! reaction'.

An 'Aha! reaction' is a brief moment of exceptional thinking where an unexpected change in one's mental perspective reveals the solution to an otherwise intractable problem. In this event-related fMRI study, subjects read incomprehensible sentences followed by solution cues that were used to evoke such a reaction by triggering an alternative interpretation of the critical concepts. For 73% of the trials, subjects attributed their failure in the initial stage of sentence presentation to "having thought about it in another direction". This behavior implies that the breaking of mental impasse is a critical component of the Aha! reaction phenomenon. During the Aha! reaction we observed anterior cingulate and left lateral prefrontal cortical activation, which are two areas known to mediate cognitive conflict.