Left posterior temporal cortex is sensitive to syntax within conceptually matched Arabic expressions

Abstract

During language comprehension, the brain processes not only word meanings, but also the grammatical structure—the “syntax”—that strings words into phrases and sentences. Yet the neural basis of syntax remains contentious, partly due to the elusiveness of experimental designs that vary structure independently of meaning-related variables. Here, we exploit Arabic’s grammatical properties, which enable such a design. We collected magnetoencephalography (MEG) data while participants read the same noun-adjective expressions with zero, one, or two contiguously-written definite articles (e.g., ‘chair purple’; ‘the-chair purple’; ‘the-chair the-purple’), representing equivalent concepts, but with different levels of syntactic complexity (respectively, indefinite phrases: ‘a purple chair’; sentences: ‘The chair is purple.’; definite phrases: ‘the purple chair’). We expected regions processing syntax to respond differently to simple versus complex structures. Single-word controls (‘chair’/‘purple’) addressed definiteness-based accounts. In noun-adjective expressions, syntactic complexity only modulated activity in the left posterior temporal lobe (LPTL), ~ 300 ms after each word’s onset: indefinite phrases induced more MEG-measured positive activity. The effects disappeared in single-word tokens, ruling out non-syntactic interpretations. In contrast, left anterior temporal lobe (LATL) activation was driven by meaning. Overall, the results support models implicating the LPTL in structure building and the LATL in early stages of conceptual combination.

Minimal phrase composition revealed by intracranial recordings

“…Our findings are concordant with recent results and models implicating the pSTS in phrase composition (Nelson et al, 2017;Flick and Pylkkänen, 2020;Matchin and Hickok, 2020;Murphy, 2020;Law and Pylkkänen, 2021;Matar et al, 2021); producing hierarchically organized functional morphemes (Lee et al, 2018); sign language comprehension (Trettenbrein et al, 2021); cross-linguistic reading competence (Feng et al, 2020).…”

Inflection across Categories: Tracking Abstract Morphological Processing in Language Production with MEG

“…2016 ). In our own work, we have observed “pure” effects of structure only in the left posterior temporal cortex ( Flick and Pylkkänen 2020 ; Law and Pylkkänen 2021 ; Matar et al. 2021 ).…”

“…With regard to our paradigm, it is important to note that words produced in verb contexts completed a sentence (e.g., “He dreams”), while words produced in noun contexts (“Two dreams”) did not. In fact, recent MEG work on Standard Arabic showed increased activity in the left posterior temporal lobe for length- and lexically matched sentences versus noun phrases ( Matar et al. 2021 ).…”

Semantic and syntactic information processing during auditory language comprehension: A spectral stereo-EEG approach

“…This in line with the role of the anterior temporal lobe described in the literature. Indeed, the temporal pole has been shown to play a role in semantic processing and language comprehension in neuroimaging 16,43,44 , MEG 45 and neuropsychological 46,47 studies (see also 48 ).…”