High gamma response tracks different syntactic structures in homophonous phrases

Area of Science:

• Neuroscience
• Linguistics
• Cognitive Science

Background:

• Syntax, the grammatical structure of language, is uniquely human and typically inseparable from spoken words.
• Distinguishing syntactic processing from acoustic properties in the brain is challenging due to the inherent link between sound and meaning.

Purpose of the Study:

• To investigate the neural correlates of syntactic processing by creating acoustically identical phrases with distinct grammatical functions.
• To determine if the brain differentiates between noun phrases (NP) and verb phrases (VP) with identical acoustic components.

Main Methods:

• Stereo-electroencephalography (SEEG) recordings were performed in epileptic patients.
• Homophonous phrases, differing only in syntactic role (NP vs. VP), were presented to participants.
• High gamma band activity (150–300 Hz) was analyzed for differential electrophysiological responses.

Main Results:

• Significant differences in high gamma band activity were observed between noun phrases and verb phrases across multiple cortical areas.
• These distinct neural signatures were detected in both language-dominant and non-dominant hemispheres.
• The findings demonstrate that the brain distinguishes syntactic structure even when acoustic information is identical.

Conclusions:

• The brain exhibits distinct electrophysiological responses to syntactic structures, independent of acoustic variations.
• High gamma band activity is a key neural marker for differentiating syntactic roles (NP vs. VP).
• This research contributes to the neural decoding of linguistic structures, offering insights into the brain's language processing mechanisms.