Cracking the language code: Neural mechanisms underlying speech parsing
Cracking the language code: Neural mechanisms underlying speech parsing
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DOI：
10.1523/jneurosci.5501-05.2006
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发表时间：
2006-07-19
影响因子：
5.3
通讯作者：
Dapretto, Mirella
中科院分区：
文献类型：
--
作者：
McNealy, Kristin;Mazziotta, John C.;Dapretto, Mirella
分词，即在连续语音中检测词的边界，是语言学习的一个重要方面。先前对婴儿和成人的研究表明，仅根据输入提供的统计和语音线索，就可以很容易地对语音流进行分割。研究人员利用功能性磁共振成像（fMRI）技术，在线检测了被试在听三种音节串连流时的分词神经基础。三种音节串连流分别包含统计规律、统计规律和语音线索，以及没有线索。尽管参与者无法明确地检测语音流之间的差异，但不同条件下的神经活动差异显著，只有当参与者听包含统计规律的流，特别是包含语音线索的流时，颞叶皮层的左偏侧信号才会增加。在第二项功能磁共振成像研究中，为了验证分词是否已经隐性地发生，参与者听了在他们刚刚听到的语音流中以不同频率出现的三音节组合（“单词”45次；“部分单词”15次；“非单词”1次）。在比较单词和部分单词时，可以可靠地观察到左下额回和中额回的活动更大，而在比较部分单词和非单词时，活动的程度较小。这些区域的活动与参与者的快速听觉处理技能正相关，被用来索引对单词边界的内隐检测。这些发现提供了一个成熟大脑在线分词的神经特征，并为研究语言学习过程中处理语音线索的神经结构的发育变化提供了一个初步模型。
Word segmentation, detecting word boundaries in continuous speech, is a critical aspect of language learning. Previous research in infants and adults demonstrated that a stream of speech can be readily segmented based solely on the statistical and speech cues afforded by the input. Using functional magnetic resonance imaging (fMRI), the neural substrate of word segmentation was examined on-line as participants listened to three streams of concatenated syllables, containing either statistical regularities alone, statistical regularities and speech cues, or no cues. Despite the participants' inability to explicitly detect differences between the speech streams, neural activity differed significantly across conditions, with left-lateralized signal increases in temporal cortices observed only when participants listened to streams containing statistical regularities, particularly the stream containing speech cues. In a second fMRI study, designed to verify that word segmentation had implicitly taken place, participants listened to trisyllabic combinations that occurred with different frequencies in the streams of speech they just heard ("words," 45 times; "partwords,"15 times; "nonwords,"once). Reliably greater activity in left inferior and middle frontal gyri was observed when comparing words with partwords and, to a lesser extent, when comparing partwords with nonwords. Activity in these regions, taken to index the implicit detection of word boundaries, was positively correlated with participants' rapid auditory processing skills. These findings provide a neural signature of on-line word segmentation in the mature brain and an initial model with which to study developmental changes in the neural architecture involved in processing speech cues during language learning.