No evidence for functional distinctions across fronto-temporal language regions in their temporal receptive windows

Abstract

AbstractThe “core language network” consists of left temporal and frontal regions that are selectively engaged in linguistic processing. Whereas the functional differences across these regions have long been debated, many accounts propose distinctions in terms of representational grain-size—e.g., wordsvs.sentences—or processing time-scale, i.e., operating on local linguistic featuresvs.larger spans of input. Indeed, the topography of language regions appears to overlap with a cortical hierarchy reported by Lerner et al. (2011) wherein mid-posterior temporal regions are sensitive to low-level features of speech, surrounding areas—to word-level information, and inferior frontal areas—to sentence-level information and beyond. However, the correspondence between the language network and this hierarchy of “temporal receptive windows” (TRWs) is difficult to establish because the precise anatomical locations of language regions vary across individuals. To directly test this correspondence, we first identified language regions in each participant with a task-based localizer, which confers high functional resolution to the study of TRWs (traditionally based on stereotactic coordinates); then, we characterized regional TRWs with the naturalistic story listening paradigm of Lerner et al. (2011), which augments task-based characterizations of the language network by more closely resembling comprehension “in the wild”. We find no region-by-TRW interactions across temporal and inferior frontal regions, which are all sensitive to both word-level and sentence-level information. Therefore, the language network as a whole constitutes a unique stage of information integration within a broader cortical hierarchy.HighlightsLanguage regions are identified with task-based, participant-specific localization.A progressively scrambled naturalistic story probes regional processing timescales.Widespread sensitivity to scrambling at the timescales of both words and sentences.No processing timescale distinctions across temporal and inferior-frontal regions.These regions all occupy a common, unique stage in a broader processing hierarchy.