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Dynamic Neural Reorganization Underlying Speech Disambiguation

Poster Session E - Monday, March 9, 2026, 2:30 – 4:30 pm PDT, Fairview/Kitsilano Ballroom

Francis Pingfan Chien¹ (), Yu Tsao², Po-Jang Hsieh³; ¹Taiwan International Graduate Program in Interdisciplinary Neuroscience, National Taiwan University and Academia Sinica, Taipei, Taiwan, ²Research Center for Information Technology Innovation, Academic Sinica, Taiwan, ³Department of Psychology, National Taiwan University, Taipei, Taiwan

Prior exposure to a clean speech often enhances understanding when that speech is later heard in noise. We examined how clean exposure alters behavior, fMRI multivoxel patterns, and functional connectivity for Mandarin sentences masked at −12 dB SNR. In the scanner, each sentence appeared sequentially as Pre-Noisy, Clean, and then Post-Noisy across six runs with 24 sentences, and 21 participants reported comprehension on every trial. Behaviors improved significantly, with Clean higher than Pre and Post higher than Pre. Univariate effects spanned language regions, including superior and middle temporal gyri (STG/MTG), supramarginal gyrus (SMG), angular gyrus (AG), inferior frontal gyrus (IFG), precentral gyrus (PreCG), and dorsolateral prefrontal cortex (DLPFC). Support vector machine–based multivoxel pattern analysis (MVPA-SVM) decoded Pre, Clean, and Post above chance across STG, MTG, SMG, AG, IFG, PreCG, and DLPFC. Representational similarity analysis (RSA) showed that cross-condition alignment shifted after clean exposure, with Post-to-Clean exceeding Pre-to-Clean in STG, MTG, SMG, and IFG. A t-distributed stochastic neighbor embedding (t-SNE) revealed that, in STG/MTG, the Clean condition clusters at the center, Post-Noisy surrounds that center, and Pre-Noisy lies farther out; in IFG, each sentence forms its own cluster, with Clean and Post-Noisy close together and Pre-Noisy more distant. Functional connectivity decreased between temporal and sensorimotor/visuospatial regions in Clean compared with Pre, and increased between IFG and parietal/sensorimotor regions in Post compared with Clean. This pattern suggests that clean exposure creates a stable reference representation in the temporal cortex. When noise returns, a lateral IFG–parietal–sensorimotor circuit reconstructs the degraded input.

Topic Area: LANGUAGE: Semantic