Work

The cortical architecture representing the linguistic hierarchy of the conversational speech

Year: 2025

Type: article

Abstract: • The bi-directional conversational speech showed a linguistic hierarchy. • A cortical architecture supports the linguistic hierarchy at the dyadic level. • The cortical architecture was shared by interlocutors. • The cortical architecture was not found in the individual interlocutor. • Different levels of the linguistic hierarchy could be selectively impacted. Recent studies demonstrate that the brain parses natural language into smaller units represented in lower-order regions and larger units in higher-order regions. Most of these studies, however, have been conducted on unidirectional narrative speech, leaving the linguistic hierarchy and its cortical representation in bidirectional conversational speech unexplored. To address this gap, we simultaneously measured brain activity from two individuals using functional near-infrared spectroscopy (fNIRS) hyperscanning while they engaged in a naturalistic conversation. Using a Pre-trained Language Model (PLM) and Representational Similarity Analysis (RSA), we demonstrated that conversational speech, jointly produced by two interlocutors in a turn-taking manner, exhibits a linguistic hierarchy, characterized by a boundary effect between linguistic units and an incremental context effect. Furthermore, a gradient pattern of shared cortical representation of the linguistic hierarchy was identified at the dyadic rather than the individual level. Interpersonal neural synchronization (INS) in the left superior temporal cortex was associated with turn representation, whereas INS in the medial prefrontal cortex was linked to topic representation. These findings further validated the distinctiveness of linguistic units of different sizes. Together, our results provide original evidence for the linguistic hierarchy and the underlying cortical architecture during a naturalistic conversation, extending the hierarchical nature of natural language from unidirectional narrative speech to bidirectional conversational speech.

Source: NeuroImage

DOI: 10.1016/j.neuroimage.2025.121180

Authors: Ruhuiya Aili, Siyuan Zhou, Xinran Xu, Xiangyu He, Chunming Lu

Institutions: Beijing Normal University, State Key Laboratory of Cognitive Neuroscience and Learning, Sichuan Normal University

Language: English

Topic: Neurobiology of Language and Bilingualism

Subfield: Cognitive Neuroscience

Field: Neuroscience

Domain: Life Sciences

Open Access status: gold

Estimated APC paid: $3,540

Funder: National Natural Science Foundation of China