The cortical organization of lexical knowledge: A dual lexicon model of spoken language processing

Current accounts of spoken language assume the existence of a lexicon where wordforms are stored and interact during spoken language perception, understanding and production. Despite the theoretical importance of the wordform lexicon, the exact localization and function of the lexicon in the broader context of language use is not well understood. This review draws on evidence from aphasia, functional imaging, neuroanatomy, laboratory phonology and behavioral results to argue for the existence of parallel lexica that facilitate different processes in the dorsal and ventral speech pathways. The dorsal lexicon, localized in the inferior parietal region including the supramarginal gyrus, serves as an interface between phonetic and articulatory representations. The ventral lexicon, localized in the posterior superior temporal sulcus and middle temporal gyrus, serves as an interface between phonetic and semantic representations. In addition to their interface roles, the two lexica contribute to the robustness of speech processing.

► Spoken language processing relies on parallel lexica in the dorsal and ventral speech streams.
► The pMTG mediates the mapping between sound and meaning in the ventral stream lexicon.
► The SMG mediates the mapping between sound and articulation in the dorsal stream lexicon.
► Both lexica may play a role in speech perception and production.
► Uniquely lexical properties influence behavioral/neural measures of both streams.