Neural Basis of Metaphor Congruency Effect: Evidence from Functional Near-infrared Spectroscopy with a Motor-Stroop Task

A great body of research has investigated the metaphor congruency effect in the grounding of abstract concepts, showing different responses following abstract concepts presented in metaphor incongruent compared with congruent conditions (e.g., powerful words paired with lower vs. upper positions). However, the neural basis of the effect has not been addressed. Here, we combined functional near-infrared spectroscopy with a novel motor-Stroop task requiring participants to read aloud high- and low-power words while performing up-down arm movements, which was consistent or inconsistent with spatial metaphors of power. Results showed that the bilateral inferior frontal gyrus was more strongly activated in the incongruent as compared to congruent conditions for high-power words, revealing the critical role of the bilateral inferior frontal gyrus in the metaphor congruency effect in language-motor associations. In addition, the motor-Stroop task we developed provides a useful paradigm to examine the metaphor congruency effect in the embodied processing of abstract concepts.