Browsing by Author "Xu, Yisheng"

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    Activation of the left planum temporale in pitch processing is shaped by language experience
    (Wiley, 2005-07-20) Xu, Yisheng; Gandour, Jackson; Talavage, Thomas; Wong, Donald; Dzemidzic, Mario; Tong, Yunxia; Li, Xiaojian; Lowe, Mark; Anatomy and Cell Biology, School of Medicine
    Implicit, abstract knowledge acquired through language experience can alter cortical processing of complex auditory signals. To isolate prelexical processing of linguistic tones (i.e., pitch variations that convey part of word meaning), a novel design was used in which hybrid stimuli were created by superimposing Thai tones onto Chinese syllables (tonal chimeras) and Chinese tones onto the same syllables (Chinese words). Native speakers of tone languages (Chinese, Thai) underwent fMRI scans as they judged tones from both stimulus sets. In a comparison of native vs. non‐native tones, overlapping activity was identified in the left planum temporale (PT). In this area a double dissociation between language experience and neural representation of pitch occurred such that stronger activity was elicited in response to native as compared to non‐native tones. This finding suggests that cortical processing of pitch information can be shaped by language experience and, moreover, that lateralized PT activation can be driven by top‐down cognitive processing.
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    Neural basis of first and second language processing of sentence-level linguistic prosody
    (Wiley, 2006-05-22) Gandour, Jackson; Tong, Yunxia; Talavage, Thomas; Wong, Donald; Dzemidzic, Mario; Xu, Yisheng; Li, Xiaojian; Lowe, Mark; Anatomy and Cell Biology, School of Medicine
    A fundamental question in multilingualism is whether the neural substrates are shared or segregated for the two or more languages spoken by polyglots. This study employs functional MRI to investigate the neural substrates underlying the perception of two sentence‐level prosodic phenomena that occur in both Mandarin Chinese (L1) and English (L2): sentence focus (sentence‐initial vs. ‐final position of contrastive stress) and sentence type (declarative vs. interrogative modality). Late‐onset, medium proficiency Chinese‐English bilinguals were asked to selectively attend to either sentence focus or sentence type in paired three‐word sentences in both L1 and L2 and make speeded‐response discrimination judgments. L1 and L2 elicited highly overlapping activations in frontal, temporal, and parietal lobes. Furthermore, region of interest analyses revealed that for both languages the sentence focus task elicited a leftward asymmetry in the supramarginal gyrus; both tasks elicited a rightward asymmetry in the mid‐portion of the middle frontal gyrus. A direct comparison between L1 and L2 did not show any difference in brain activation in the sentence type task. In the sentence focus task, however, greater activation for L2 than L1 occurred in the bilateral anterior insula and superior frontal sulcus. The sentence focus task also elicited a leftward asymmetry in the posterior middle temporal gyrus for L1 only. Differential activation patterns are attributed primarily to disparities between L1 and L2 in the phonetic manifestation of sentence focus. Such phonetic divergences lead to increased computational demands for processing L2. These findings support the view that L1 and L2 are mediated by a unitary neural system despite late age of acquisition, although additional neural resources may be required in task‐specific circumstances for unequal bilinguals.
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    Neural correlates of segmental and tonal information in speech perception
    (Wiley, 2003-10-27) Gandour, Jack; Xu, Yisheng; Wong, Donald; Dzemidzic, Mario; Lowe, Mark; Li, Xiaojian; Tong, Yunxia; Anatomy and Cell Biology, School of Medicine
    The Chinese language provides an optimal window for investigating both segmental and suprasegmental units. The aim of this cross‐linguistic fMRI study is to elucidate neural mechanisms involved in extraction of Chinese consonants, rhymes, and tones from syllable pairs that are distinguished by only one phonetic feature (minimal) vs. those that are distinguished by two or more phonetic features (non‐minimal). Triplets of Chinese monosyllables were constructed for three tasks comparing consonants, rhymes, and tones. Each triplet consisted of two target syllables with an intervening distracter. Ten Chinese and English subjects were asked to selectively attend to targeted sub‐syllabic components and make same‐different judgments. Direct between‐group comparisons in both minimal and non‐minimal pairs reveal increased activation for the Chinese group in predominantly left‐sided frontal, parietal, and temporal regions. Within‐group comparisons of non‐minimal and minimal pairs show that frontal and parietal activity varies for each sub‐syllabic component. In the frontal lobe, the Chinese group shows bilateral activation of the anterior middle frontal gyrus (MFG) for rhymes and tones only. Within‐group comparisons of consonants, rhymes, and tones show that rhymes induce greater activation in the left posterior MFG for the Chinese group when compared to consonants and tones in non‐minimal pairs. These findings collectively support the notion of a widely distributed cortical network underlying different aspects of phonological processing. This neural network is sensitive to the phonological structure of a listener's native language.