The Influence of Context on Hemispheric Recruitment during Metaphor Processing

Although the left hemisphere's prominence in language is well established, less emphasis has been placed on possible roles for the right hemisphere. Behavioral, patient, and neuroimaging research suggests that the right hemisphere may be involved in processing figurative language. Additionally, research has demonstrated that context can modify language processes and facilitate comprehension. Here we investigated how figurativeness and context influenced brain activation, with a specific interest in right hemisphere function. Previous work in our laboratory indicated that novel stimuli engaged right inferior frontal gyrus (IFG) and that both novel and familiar metaphors engaged right IFG and right temporal pole. The graded salience hypothesis proposes that context may lessen integration demands, increase the salience of metaphors, and thereby reduce right hemisphere recruitment for metaphors. In the present study, fMRI was used to investigate brain function, whereas participants read literal and metaphoric sentences that were preceded by either a congruent or an incongruent literal sentence. Consistent with prior research, all sentences engaged traditional left hemisphere regions. Differences between metaphors and literal sentences were observed, but only in the left hemisphere. In contrast, a main effect of congruence was found in the right IFG, the right temporal pole, and the dorsal medial pFC. Partially consistent with the graded salience hypothesis, our results highlight the strong influence of context on language, demonstrate the importance of the right hemisphere in discourse, and suggest that, in a wider discourse context, congruence has a greater influence on right hemisphere recruitment than figurativeness.