No abstract

Non-arbitrary mapping between the sound of a word and its meaning, termed sound symbolism, is commonly studied through correspondences between sounds and visual shapes, e.g., auditory pseudowords, like 'mohloh' and 'kehteh', are matched to rounded and pointed visual shapes, respectively. Here, we used functional magnetic resonance imaging (fMRI) to investigate the neural basis of the pseudoword-shape correspondence. During scanning, right-handed participants (n = 22) encountered audiovisual stimuli consisting of a simultaneously presented visual shape (rounded or pointed) and an auditory pseudoword ('mohloh' or 'kehteh') and indicated via a right-handed keypress whether the stimuli matched or not. Reaction times were faster for congruent than incongruent stimuli. On a univariate contrast between congruent and incongruent stimuli, activity was greater in the left primary auditory and somatosensory cortices, left anterior fusiform/parahippocampal and right mid-cingulate gyri, and caudate nuclei bilaterally for the congruent condition; and at left precentral, left supplementary motor and bilateral anterior insular cortical foci in the incongruent condition. Multivoxel pattern analysis revealed higher classification accuracy in the pars opercularis of the left inferior frontal gyrus (Broca's area), the left supramarginal gyrus, and the right mid-occipital gyrus for the audiovisual stimuli when bimodally congruent than when incongruent. Visual and auditory cortices robustly differentiated between the two visual/auditory stimuli, respectively, regardless of audiovisual congruency. Frontoparietal cortical regions distinguished congruent from incongruent stimulus pairs, independent of the visual or auditory features. Taken together, these findings indicate that sound-symbolic correspondences engage neural processes in sensory, motor, and language systems.