Differential cortical contribution of syntax and semantics: An fMRI study on two-word phrasal processing

Area of Science:

• Neuroscience
• Psycholinguistics
• Cognitive Science

Background:

• Understanding how the brain combines words into meaningful phrases and sentences is crucial for deciphering language processing.
• The specific neural mechanisms underlying basic syntactic and semantic combination remain incompletely understood.
• Differentiating brain networks for syntax and semantics at the earliest stages of linguistic combination is essential.

Purpose of the Study:

• To disentangle the distinct neural networks supporting syntactic versus semantic processing in two-word combinations.
• To investigate how manipulating grammatical class influences brain activity related to syntax and semantics.
• To identify specific brain regions involved in early-stage syntactic and semantic computations.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was employed to measure brain activity.
• Participants processed two-word combinations with varying combinatorial loads (determiner-noun vs. adjective-noun phrases).
• Analysis focused on differentiating neural responses associated with syntax-driven (determiner-noun) and semantics-driven (adjective-noun) processing.

Main Results:

• Syntactic processing predominantly activated the ventral inferior frontal gyrus (IFG), frontal operculum (FOP), and anterior insula (aINS).
• Semantic processing engaged the anterior dorsal left IFG and the left angular gyrus (AG).
• Fine-grained analysis revealed the ventral part of Brodmann area 44 (BA44) is sensitive to function-word-driven syntactic computations.

Conclusions:

• Syntactic and semantic contributions to phrasal formation are separable at a basic two-word level.
• Distinct, non-overlapping cortical areas support syntactic and semantic processing.
• Confirms the role of ventral IFG in constructing syntactically valid phrases and anterior IFG/AG in conceptual semantics.