The language network supports both lexical access and sentence generation during language production

Abstract

AbstractA network of left frontal and temporal brain regions has long been implicated in language comprehension and production. However, because of relatively fewer investigations of language production, the precise role of this ‘language network’ in production-related cognitive processes remains debated. Across four fMRI experiments that use picture naming/description to mimic the translation of conceptual representations into words and sentences, we characterize the response of the language regions to production demands. In line with prior studies, sentence production elicited strong responses throughout the language network. Further, we report three novel results. First, we demonstrate that production-related responses in the language network are robust to output modality (speaking vs. typing). Second, the language regions respond to both lexical access and sentence-generation demands. This pattern implies strong integration between lexico-semantic and combinatorial processes, mirroring the picture that has emerged in language comprehension. Finally, some have previously hypothesized the existence of production-selective mechanisms given that syntactic encoding is a critical part of sentence production, whereas comprehension is possible even when syntactic cues are degraded or absent. Contrary to this hypothesis, we find no evidence of brain regions that selectively support sentence generation. Instead, language regions respond overall more strongly during production than during comprehension, which suggests that production incurs a greater cost for the language network. Together, these results align with the idea that language comprehension and production draw on the same knowledge representations, which are stored in the language-selective network and are used both to interpret linguistic input and generate linguistic output.