Lists with and without Syntax: A New Approach to Measuring the Neural Processing of Syntax

Area of Science:

• Neurobiology
• Linguistics
• Cognitive Neuroscience

Background:

• Understanding the neurobiology of syntax is challenging due to the difficulty in isolating syntactic processing from semantic content.
• Previous research often struggles to manipulate syntax independently of meaning and phrasal combinatorics.
• A novel methodological approach is needed to disentangle the neural correlates of syntactic structure and lexical semantics.

Purpose of the Study:

• To investigate the neural basis of syntactic processing by controlling for semantic and combinatorial confounds.
• To differentiate the brain regions involved in processing global sentence structure versus associative word meaning.
• To characterize the distinct neural signatures of syntax and semantics in language comprehension.

Main Methods:

• Utilized magnetoencephalography (MEG) to measure brain activity.
• Employed word lists embedded within sentences and longer lists as stimuli to isolate syntactic structure.
• Varied semantic association strength between list items to assess its neural correlates.

Main Results:

• Sentence-embedded lists significantly increased MEG activity in the left inferior frontal cortex, left anterior temporal lobe, and left posterior temporal cortex (250-400 ms).
• Semantic association strength modulated activity in the left temporoparietal cortex around 400 ms.
• A clear dissociation was observed: frontotemporal networks responded to syntactic structure, while temporoparietal regions tracked associative semantics.

Conclusions:

• The frontotemporal language network can be driven by the presence of global sentence structure, even without local semantic composition.
• Associative semantics engages distinct, more posterior neural regions, specifically the left temporoparietal junction.
• This study provides a novel characterization of the distinct neural signatures for syntactic structure versus word meaning in the brain.