Enhanced insightfulness and neural activation induced by metaphorical solutions to appropriate mental distress problems.

Although the neural correlates of novelty and appropriateness of creative insight during cognitive tasks have been investigated in several studies, they have not been examined during mental distress in a psychotherapeutic setting. This study aimed to reveal the promoting effects of novelty and appropriateness processing on therapeutic insight in a micro-psychotherapeutic setting. We examined the effects of appropriateness (between-subject factor: appropriateness group, 20 participants; inappropriateness group, 21 participants) by manipulating the preceding negative scenarios that either fit or did not fit the subsequent solutions, and those of novelty (within-subject factor) by varying the linguistic expressions for describing solutions (metaphorical, literal, or problem-restatement). Event-related functional magnetic resonance images were collected. We found the following effects: an interactive effect of the two factors on insightfulness and activation in the bilateral hippocampus and amygdala, right superior frontal gyrus, and left superior/middle temporal gyrus; a simple effect of novelty on activation in the bilateral inferior frontal gyrus, fusiform gyrus, and inferior/middle occipital gyrus; and a simple effect of appropriateness on activation in the left inferior parietal lobule. Our findings indicate that solutions with high novelty and appropriateness generate the highest levels of therapeutic insightfulness as well as the strongest activation in the hippocampus and amygdala, which may be involved in episodic memory encoding.