Cross-modal comparisons of stimulus specificity and commonality in phonological processing

•Regions critical for phonological processing are either stimulus specific or supramodal.•High degree of modality specificity is observed in visual and auditory networks.•Supramodal region is identified in the left middle temporal gyrus and superior temporal sulcus.

Phonological processing is a fundamental ability which underlies language comprehension. Functional neuroanatomy of phonology constitutes a matter of ongoing debate. In the present study, subjects performed visual (rhyme detection) and auditory (identification of spoken words starting with a given consonant) tasks that were contrasted with matched nonverbal tasks. We identified regions critical for phonological processing which were either stimulus specific or supramodal. The results revealed a high degree of modality specificity in both visual and auditory networks. Moreover, we observed a modality independent region in the left middle temporal gyrus (MTG)/superior temporal sulcus (STS), between a more anterior temporal area with auditory specificity and a more posterior temporal area with visual specificity. This dissociation in functional neuroanatomy suggests that this area may be a core region for supramodal phonological processing, acting as a gateway between spatially separate, but stimulus specific, phonological processes and more general linguistic functions.