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A comparison of top-down effects on phonological processing induced by lexical context and by situational language context: An investigation using electrocortikography and magnetoencephalography

词汇语境和情境语言语境对语音处理的自上而下影响的比较：使用皮层电图和脑磁图的调查

基本信息

批准号：
301795112
负责人：
Dr. Yulia Oganian
金额：
--
依托单位：
Werner Reichardt-Centrum für integrative Neurowissenschaften (CIN)
依托单位国家：
德国
项目类别：
Research Fellowships
财政年份：
2016
资助国家：
德国
起止时间：
2015-12-31 至 2017-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/301795112?language=en
关键词：
comparison top down effects phonological

项目摘要

A word can sound different depending on the speaker or background noise. Yet, we are highly skilled in extracting stable percepts from noisy and variable acoustic signals. It is well established that this ability is based on the recognition of phonemes, the smallest speech units that alter meaning (consonants and vowels), localized to the left superior temporal gyrus (STG). A fundamental principle of phoneme recognition is that acoustically varying inputs are mapped fast and effortlessly to a finite number of phonemic categories. However, predictions originating in proximate inputs or in situational information, such as the input language, can alter this mapping. An example for such predictive coding are lexical top-down effects that can entail categorization of a phonetic token preceded by /woo/ as /d/, but as /t/ when preceded by /boo/, resulting in /wood/ and /boot/. Similarly, due to acoustic differences between these phonemes across languages, the same token might be perceived as /d/ in an English context, but as /t/ in a Spanish context. It is currently unknown what neural mechanisms mediate such predictive effects on phonemic representations in the left STG, although describing these mechanisms is pertinent to neural models of speech recognition. Indeed, until recently, such endeavors were hindered by the crude resolution of available methods in human neuroscience, lacking sufficient spatial (e.g. magnetic encephalography, MEG) or temporal (magnetic resonance imaging) resolution. This changed with the development of human electrocorticography (ECoG). With ECoG, neural activity is recorded subdurally from a confined cortical area with high spatiotemporal resolution. I propose to employ whole-brain MEG and ECoG of posterior STG in 5 studies, designed to investigate the neural mechanisms mediating the effects of lexical and situational language context on phoneme recognition. Study 1 will employ MEG to describe the timing of integration between acoustic input and lexical expectations in phonemic categorization. Study 2 will employ ECoG to further identify spatiotemporal changes underlying these lexical top-down effects. Studies 3 and 4 will elucidate the differences between neural encoding of first (L1) and second (L2) language phonology and phonemic sequence probabilities. For this, ECoG signal will be recorded in Spanish-English bilinguals listening to sentences in their L1 and L2. A fifth MEG study will compare effects of lexical and language contexts on phonemic categorization. Subjects will perform phonemic categorizations on tokens embedded in either lexical or only language context in L1 and L2, thus making these two sources of predictions independent. The crucial contrast between conditions in which lexical and language context will induce equal percepts will directly pit their underlying mechanisms against each other. Overall, this research program will set the foundations for neural models of predictive effects on speech perception.

一个单词听起来会因说话者或背景噪音而不同。然而，我们在从噪声和可变的声学信号中提取稳定的感知方面非常熟练。众所周知，这种能力是基于对音素的识别，音素是改变意义的最小语音单位（辅音和元音），位于左上级颞回（STG）。音素识别的一个基本原理是，声学上变化的输入被快速且毫不费力地映射到有限数量的音素类别。然而，源自近似输入或情境信息（如输入语言）的预测可能会改变这种映射。这样的预测编码的示例是词汇自上而下的效果，其可能需要将前面是/woo/的语音标记分类为/d/，但是当前面是/boo/时分类为/t/，从而导致/wood/和/靴子/。类似地，由于不同语言中这些音素之间的声学差异，相同的标记在英语上下文中可能被视为/d/，但在西班牙语上下文中可能被视为/t/。目前尚不清楚是什么神经机制介导了这种预测效果的音素表示在左STG，虽然描述这些机制是相关的语音识别的神经模型。事实上，直到最近，这种努力受到人类神经科学中可用方法的粗糙分辨率的阻碍，缺乏足够的空间（例如磁脑描记术，MEG）或时间（磁共振成像）分辨率。这种情况随着人类皮层电图（ECoG）的发展而改变。使用ECoG，从具有高时空分辨率的有限皮层区域记录硬膜下神经活动。本研究拟采用5项研究，分别采用全脑脑MEG和STG后部ECoG，探讨词汇语境和情景语境对音素识别影响的神经机制。研究一将使用MEG来描述音位分类中声学输入和词汇期望之间的整合时间。研究二将采用皮层脑电图进一步识别这些词汇自上而下效应背后的时空变化。研究3和4将阐明第一语言（L1）和第二语言（L2）语音和音素序列概率的神经编码之间的差异。为此，ECoG信号将被记录在西班牙语-英语双语者听句子在他们的L1和L2。第五项MEG研究将比较词汇和语言语境对音位分类的影响。受试者将对嵌入L1和L2中的词汇或仅语言上下文中的标记进行音素分类，从而使这两个预测源独立。词汇语境和语言语境诱导相同感知的条件之间的关键对比将直接使它们的潜在机制相互对立。总的来说，这项研究计划将为语音感知预测效果的神经模型奠定基础。