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The role of basal ganglia in Chinese syntactic ambiguity resolution
Poster Session D, Saturday, October 26, 10:30 am - 12:00 pm, Great Hall 3 and 4
Yingying Tan1, Ran Zhang1, Xiaolin Zhou1, Zheng Ye2; 1Shanghai International Studies University, Shanghai, China, 2Institute of Neuroscience, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, China
Incremental language comprehension requires readers to confront temporary ambiguity and quickly extract correct meaning from the input. Previous studies have shown that ambiguity resolution activates various brain regions within the classic language network, including the left IFG, left MTG, and bilateral MFG [1, 2]. However, the role of subcortical structures, such as basal ganglia (BG), in ambiguity resolution is less understood. This study aims to investigate the role of the BG in processing Chinese ambiguous sentences and whether this role is modulated by individuals’ cognitive functions like working memory (WM) and response inhibition. Sixty-four healthy participants were tested in a garden-path experiment with functional MRI (fMRI). Participants’ neural activity was recorded while they read Chinese sentences containing ambiguous structures in the form of verb phrase (VP) + noun phrase1 (NP1) + “de” + NP2. For example, the phrase "bite hunter de dog" can be interpreted as either a VP that means “ (someone) bit the hunter’s dog”, or a NP that means “the dog who bit the hunter”. Seventy-two ambiguous structures were selected, with half favoring a VP interpretation and the other half favoring an NP interpretation. For each ambiguous sentence, a matched unambiguous sentence was constructed by replacing the NP1 with an adjective (e.g., bite smart de dog). Thus, ambiguity (ambiguous vs. unambiguous) and structure type (NP-preferred vs. VP-preferred) were crossed, resulting in four experimental conditions. Additionally, the same participants completed a series of behavioral tests to measure their WM and inhibition ability. Our results replicated previous findings on garden-path sentences, showing that ambiguity resolution primarily activates the classic frontal-temporal language network. Moreover, participants were less accurate in answering comprehension questions following an NP-preferred structure than a VP-preferred structure, accompanied by significant activation in the bilateral supramarginal gyrus and left precuneus. Since NP interpretation is the dominant one with higher occurrence for the ambiguous structure used [3], we suggest that these regions may be involved in processing canonical word order. Furthermore, there was a significant interaction between ambiguity and structure type. For the NP-preferred structure, the ambiguous sentences elicited statistically higher activation than unambiguous sentences in the bilateral MFG, right superior frontal gyrus, and left precentral gyrus, whereas these regions did not show significant activation for ambiguity processing of sentences with a VP-preferred structure. We suggest that these regions might be involved in syntactic reanalysis when canonical word order is violated. Most importantly, results from the ROI analysis showed that the left caudate, especially its anterior part, was sensitive to ambiguity resolution, as it showed greater activation for ambiguous sentences than unambiguous ones. However, our preliminary results did not find any correlation between individual differences in cognitive measures and BG activation levels. Our results demonstrate that both the cerebral cortex and BG are involved in ambiguity resolution during sentence processing. [1] Mestres-Missé et al., 2012. Neuroimage. [2] Rodd et al., 2010. Neuropsychologia. [3] Zhang, et al., 2000. Acta Psychologica Sinica. *The first two authors contribute equally to the work.
Topic Areas: Syntax and Combinatorial Semantics, Reading