Lists with and without syntax: A new approach to measuring the neural processing of syntax

ABSTRACT In the neurobiology of language, a fundamental challenge is deconfounding syntax from semantics. Changes in syntactic structure usually correlate with changes in meaning. We approached this challenge from a new angle. We deployed word lists, which are usually the unstructured control in studies of syntax, as both the test and the control stimulus. Three-noun lists ( lamps, dolls, guitars ) were embedded in sentences ( The eccentric man hoarded lamps, dolls, guitars …) and in longer lists ( forks, pen, toilet, rodeo, graves, drums, mulch, lamps, dolls, guitars …). This allowed us to perfectly control both lexical characteristics and local combinatorics: the same words occurred in both conditions and in neither case did the list items locally compose into phrases (e.g. ‘ lamps ’ and ‘ dolls ’ do not form a phrase). But in one case, the list partakes in a syntactic tree, while in the other, it does not. Being embedded inside a syntactic tree increased source-localized MEG activity at ~250-300ms from word onset in the left inferior frontal cortex, at ~300-350ms in the left anterior temporal lobe and, most reliably, at ~330-400ms in left posterior temporal cortex. In contrast, effects of semantic association strength, which we also varied, localized in left temporo-parietal cortex, with high associations increasing activity at around 400ms. This dissociation offers a novel characterization of the structure vs. meaning contrast in the brain: The fronto-temporal network that is familiar from studies of sentence processing can be driven by the sheer presence of global sentence structure, while associative semantics has a more posterior neural signature. SIGNIFICANCE STATEMENT Human languages all have a syntax, which both enables the infinitude of linguistic creativity and determines what is grammatical in a language. The neurobiology of syntactic processing has, however, been challenging to characterize despite decades of study. One reason is pure manipulations of syntax are difficult to design. The approach here offers a perfect control of two variables that are notoriously hard to keep constant when syntax is manipulated: word meaning and phrasal combinatorics. The same noun lists occurred inside longer lists and sentences, while semantic associations also varied. Our MEG results show that classic fronto-temporal language regions can be driven by sentence structure even when local semantic contributions are absent. In contrast, the left temporo-parietal junction tracks associative relationships.

Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.