Continuous theta-burst stimulation demonstrates language-network-specific causal effects on syntactic processing

Hierarchical syntactic structure processing is proposed to be at the core of the human language faculty. Syntactic processing is supported by the left fronto-temporal language network, including a core area in the inferior frontal gyrus as well as its interaction with the posterior temporal lobe (i....

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Main Authors: Chenyang Gao, Junjie Wu, Yao Cheng, Yuming Ke, Xingfang Qu, Mingchuan Yang, Gesa Hartwigsen, Luyao Chen
Format: Article
Language:English
Published: Elsevier 2025-02-01
Series:NeuroImage
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Online Access:http://www.sciencedirect.com/science/article/pii/S105381192500014X
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author Chenyang Gao
Junjie Wu
Yao Cheng
Yuming Ke
Xingfang Qu
Mingchuan Yang
Gesa Hartwigsen
Luyao Chen
author_facet Chenyang Gao
Junjie Wu
Yao Cheng
Yuming Ke
Xingfang Qu
Mingchuan Yang
Gesa Hartwigsen
Luyao Chen
author_sort Chenyang Gao
collection DOAJ
description Hierarchical syntactic structure processing is proposed to be at the core of the human language faculty. Syntactic processing is supported by the left fronto-temporal language network, including a core area in the inferior frontal gyrus as well as its interaction with the posterior temporal lobe (i.e., “IFG + pTL”). Moreover, during complex syntactic processes, left IFG also interacts with executive control regions, such as the superior parietal lobule (SPL). However, the functional relevance of these network interactions is largely unclear. In particular, it remains to be demonstrated whether the language network plays a specific causal role in comparatively challenging syntactic processes, separable from the interaction between IFG and other general cognitive regions (i.e., “IFG + SPL” in the present study). The present study was designed to address this question. Thirty healthy adult Chinese native speakers underwent four continuous theta-burst stimulation (cTBS) sessions: stimulation over IFG, stimulation over IFG + pTL, stimulation over IFG + SPL, and sham stimulation over IFG + irrelevant region in a pseudo-randomized order. In each session, participants were required to label the syntactic categories of jabberwocky sequences retaining real Chinese function words (e.g., “ム了ウ” is labeled as a verb phrase (VP): “[VP [V了]N]”, similar to “ziff-ed a wug”, where “ziff” and “wug” are nonsense pseudowords, and the whole phrase is a VP). Contrasted with sham cTBS, change percentage of accuracy rates (ΔACCR%), reaction times (ΔRT%), and coefficient of variation (ΔCV%) were calculated and compared across conditions. First-order behavioral results showed a significantly higher ΔCV% after stimulating IFG + pTL compared to stimulating the IFG + SPL, indicating that syntactic processing became more unstable. Second-order representational similarity analysis (RSA) results revealed that cTBS effects on IFG + pTL selectively depended on the hierarchical embedding depth, a key measure of syntactic hierarchical complexity, whereas the effects on IFG + SPL were sensitive to the dependency length, a crucial index reflecting the working memory load. Collectively, these findings reveal the specific causal relevance of the language areas for hierarchical syntactic processing, separable from other general cognitive (such as working memory) capacities. These results shed light on the uniqueness and the specific causal role of the language network for the human language faculty, further supporting the causally separable view of the functional dissociation between the language network and the domain-general/multiple-demand network.
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spelling doaj-art-ddf66390c2434666b7d44e3c7caec3cf2025-01-23T05:26:24ZengElsevierNeuroImage1095-95722025-02-01306121014Continuous theta-burst stimulation demonstrates language-network-specific causal effects on syntactic processingChenyang Gao0Junjie Wu1Yao Cheng2Yuming Ke3Xingfang Qu4Mingchuan Yang5Gesa Hartwigsen6Luyao Chen7School of Global Education and Development, University of Chinese Academy of Social Sciences, Beijing, ChinaKey Research Base of Humanities and Social Sciences of the Ministry of Education, Academy of Psychology and Behavior, Tianjin Normal University, Tianjin, ChinaMax Planck Partner Group, School of International Chinese Language Education, Beijing Normal University, Beijing, ChinaKey Research Base of Humanities and Social Sciences of the Ministry of Education, Academy of Psychology and Behavior, Tianjin Normal University, Tianjin, ChinaMax Planck Partner Group, School of International Chinese Language Education, Beijing Normal University, Beijing, ChinaMax Planck Partner Group, School of International Chinese Language Education, Beijing Normal University, Beijing, ChinaLise Meitner Research Group Cognition and Plasticity, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany; Cognitive and Biological Psychology, Wilhelm Wundt Institute for Psychology, Leipzig University, Leipzig, GermanyMax Planck Partner Group, School of International Chinese Language Education, Beijing Normal University, Beijing, China; Department of Neuropsychology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany; Corresponding author at: NO. 19, Xinjiekouwai Str., Haidian Dist., Beijing, China.Hierarchical syntactic structure processing is proposed to be at the core of the human language faculty. Syntactic processing is supported by the left fronto-temporal language network, including a core area in the inferior frontal gyrus as well as its interaction with the posterior temporal lobe (i.e., “IFG + pTL”). Moreover, during complex syntactic processes, left IFG also interacts with executive control regions, such as the superior parietal lobule (SPL). However, the functional relevance of these network interactions is largely unclear. In particular, it remains to be demonstrated whether the language network plays a specific causal role in comparatively challenging syntactic processes, separable from the interaction between IFG and other general cognitive regions (i.e., “IFG + SPL” in the present study). The present study was designed to address this question. Thirty healthy adult Chinese native speakers underwent four continuous theta-burst stimulation (cTBS) sessions: stimulation over IFG, stimulation over IFG + pTL, stimulation over IFG + SPL, and sham stimulation over IFG + irrelevant region in a pseudo-randomized order. In each session, participants were required to label the syntactic categories of jabberwocky sequences retaining real Chinese function words (e.g., “ム了ウ” is labeled as a verb phrase (VP): “[VP [V了]N]”, similar to “ziff-ed a wug”, where “ziff” and “wug” are nonsense pseudowords, and the whole phrase is a VP). Contrasted with sham cTBS, change percentage of accuracy rates (ΔACCR%), reaction times (ΔRT%), and coefficient of variation (ΔCV%) were calculated and compared across conditions. First-order behavioral results showed a significantly higher ΔCV% after stimulating IFG + pTL compared to stimulating the IFG + SPL, indicating that syntactic processing became more unstable. Second-order representational similarity analysis (RSA) results revealed that cTBS effects on IFG + pTL selectively depended on the hierarchical embedding depth, a key measure of syntactic hierarchical complexity, whereas the effects on IFG + SPL were sensitive to the dependency length, a crucial index reflecting the working memory load. Collectively, these findings reveal the specific causal relevance of the language areas for hierarchical syntactic processing, separable from other general cognitive (such as working memory) capacities. These results shed light on the uniqueness and the specific causal role of the language network for the human language faculty, further supporting the causally separable view of the functional dissociation between the language network and the domain-general/multiple-demand network.http://www.sciencedirect.com/science/article/pii/S105381192500014XLanguage networkContinuous theta-burst stimulationSyntactic processingRepresentational similarity analysisFunction word
spellingShingle Chenyang Gao
Junjie Wu
Yao Cheng
Yuming Ke
Xingfang Qu
Mingchuan Yang
Gesa Hartwigsen
Luyao Chen
Continuous theta-burst stimulation demonstrates language-network-specific causal effects on syntactic processing
NeuroImage
Language network
Continuous theta-burst stimulation
Syntactic processing
Representational similarity analysis
Function word
title Continuous theta-burst stimulation demonstrates language-network-specific causal effects on syntactic processing
title_full Continuous theta-burst stimulation demonstrates language-network-specific causal effects on syntactic processing
title_fullStr Continuous theta-burst stimulation demonstrates language-network-specific causal effects on syntactic processing
title_full_unstemmed Continuous theta-burst stimulation demonstrates language-network-specific causal effects on syntactic processing
title_short Continuous theta-burst stimulation demonstrates language-network-specific causal effects on syntactic processing
title_sort continuous theta burst stimulation demonstrates language network specific causal effects on syntactic processing
topic Language network
Continuous theta-burst stimulation
Syntactic processing
Representational similarity analysis
Function word
url http://www.sciencedirect.com/science/article/pii/S105381192500014X
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