Neural correlates of rhyming vs. lexical and semantic fluency

Rhyming words, as in songs or poems, is a universal feature of human language across all ages. In the present fMRI study a novel overt rhyming task was applied to determine the neural correlates of rhyme production. Fifteen right-handed healthy male volunteers participated in this verbal fluency study. Participants were instructed to overtly articulate as many words as possible either to a given initial letter (LVF) or to a semantic category (SVF). During the rhyming verbal fluency task (RVF), participants had to generate words that rhymed with pseudoword stimuli. On-line overt verbal responses were audiotaped in order to correct the imaging results for the number of generated words. Fewer words were generated in the rhyming compared to both the lexical and the semantic condition. On a neural level, all language tasks activated a language network encompassing the left inferior frontal gyrus, the middle and superior temporal gyri as well as the contralateral right cerebellum. Rhyming verbal fluency compared to both lexical and semantic verbal fluency demonstrated significantly stronger activation of left inferior parietal region. Generating novel rhyme words seems to be mainly mediated by the left inferior parietal lobe, a region previously found to be associated with meta-phonological as well as sub-lexical linguistic processes.

Research Highlights
► Fewer words were generated in the rhyming compared to both the lexical and the semantic condition.
► All tasks activated the left IFG, MTG, STG and the contralateral right cerebellum.
► Rhyme generation compared to, lexical and semantic generation, highlighted left IPL.
► Generating novel rhyme words seems to be mainly mediated by the left IPL.
► The region was previously found for meta-phonological and sub-lexical processesing.