From letters to composed concepts: A magnetoencephalography study of reading

Abstract

Language comprehension requires the recognition of individual words and the combination of their meanings to yield complex concepts or interpretations. Rather than simple concatenation, this combinatory process often requires the insertion of unstated semantic material between words, based on thematic or feature knowledge of the concepts. For example, the phrase horse barn is not interpreted as a blend of a horse and a barn, but specifically a barn in which horses are kept. Mounting evidence suggests two cortical semantic hubs, in left temporoparietal and anterior temporal cortex, underpin thematic and feature concept knowledge, but much remains unclear about how these putative hubs contribute to combinatory language processing. Using magnetoencephalography, we contrasted source-localized responses to modifier-noun phrases involving thematic relations vs. feature modifications, while also examining how lower-level orthographic processing fed into responses supporting word combination. Twenty-eight participants completed three procedures examining responses to letter-strings, adjective-noun phrases, and noun-noun combinations that varied the semantic relations between words. We found that while color + noun phrases engaged the left anterior temporal lobe (150-300 ms after phrasal head), posterior temporal lobe (150-300 ms), and angular gyrus (300-450 ms), only left posterior temporal lobe responses were sensitive to implicit thematic relations between composing nouns (150-300 ms). We additionally identified a left temporo-occipital progression from orthographic to lexical processing, feeding into ventral anterior areas engaged in the combination of word meanings. Finally, by examining source signal leakage, we characterized the degree to which these responses could be distinguished from one another, using linear source estimation.

The role of left angular gyrus in the representation of linguistic composition relations

“…Moreover, the composition effect in the LATL was found both in reading and listening (Bemis & Pylkkänen, 2012) and in production (Pylkkänen, Bemis, & Elorrieta, 2014), suggesting a modality-independent function (Pylkkänen, 2020). Consistent with this, a more recent MEG study also found the involvement of the LATL in the composition process, but this was accompanied by composition-related activation in the left AG and posterior temporal lobe (Flick, Abdullah, & Pylkkanen, 2021). In addition, although the left IFG was not implicated in the MEG result mentioned above, using the functional magnetic resonance imaging (fMRI) technique, Zaccarella and colleagues found that left pars opercularis in IFG was more activated in the phrasal syntactic context (e.g., this flirk) than in the list context (e.g., apple flirk), suggesting the role of left IFG as well in housing the composition processes (Zaccarella & Friederici, 2015;Zaccarella, Meyer, Makuuchi, & Friederici, 2017).…”