Comparing two phonemic category learning mechanisms in infancy and the factors that modulate their efficacy

在婴儿出生的第一年，他们会成为感知语音差异的专家，这些语音差异被用来区分他们母语中的一个单词(音素)。这个过程被称为调谐，涉及对母语语音(语音)区别的知觉敏感度的增加，以及伴随而来的对非母语语音敏感度的下降。在这项研究中，我们比较了两种语音类别学习机制，并询问它们是否同样能产生一个音素库来区分有意义的单词。我们考察多感官信息的影响，以及每种机制在多大程度上受到关键时期的影响。我们提出了六个实验集，使用脑电和事件相关电位指数来衡量学习、神经可塑性、辨别力和语义使用。 Set I比较了两种学习机制：第一种是使用输入语音中声音的相对频率分布的统计学习，第二种是源于词形到词义的映射。在这里，以及在第2-4组中，我们测试了三组婴儿：开始调谐的(5个月)，接近结束的(9个月)，以及之后的(12个月)。在学习阶段，我们测量一个关键期可塑性的振荡生物标记物，以确定其中一个(或两个)学习机制是否受关键期的控制。在集合2中，我们增加了视觉语音线索(说话面孔)，在集合3中，我们增加了口腔-运动操作，以探索多感觉信息如何与学习和/或可塑性的时间选择相互作用。Set 4通过测试重组的语音类别是否产生可用于区分有意义的单词的可交换音素，来询问这两种学习机制是否与更高水平的语言习得一样好。为了探索可塑性是否已经完全关闭或可以重启，在组5中，我们测试了年龄较大的儿童和成年人在这两个学习过程中的表现，在组6中，我们询问外部携带伽马振荡是否可以重启成人的可塑性。 总而言之，这些研究质疑人类语言口语的根本基础，即模式化的二元性的确立。形式层面的模式化(例如，言语)如何支持意义层面的模式化。在某种程度上，这一基础成就受到早期生命关键时期的限制，并受到父母-婴儿面孔互动所固有的多感觉信息的影响，我们对语言进化的根本力量的汇合有了更深的理解。这些结果还将对被剥夺了与照顾者面对面互动的婴儿(例如，经历极端早期逆境的婴儿)以及对出生时患有感觉或运动障碍的婴儿(例如，患有视觉或口腔运动障碍的婴儿)也具有重要的应用意义。

During the first year of life, infants become specialists at perceiving the speech sound differences used to distinguish one word from another (the phonemes) in their native language. This process, termed attunement', involves an increase in perceptual sensitivity to native speech sound (phonetic) distinctions and a concomitant decrease in sensitivity to non-native ones. In this grant, we compare two phonetic category learning mechanisms and ask whether they equally well yield a phoneme repertoire to distinguish meaningful words. We examine the influence of multisensory information, and the extent to which each mechanism is gated by critical periods. We propose six experimental sets, using EEG and ERP indices to measure learning, neural plasticity, discrimination, and semantic use. Set I compares two learning mechanisms: the first using statistical learning of relative frequency distribution of sounds in input speech, and the second rooted in word form-to-meaning mappings. Here, as well as in Sets 2-4, we test three groups of infants: those beginning attunement (5 months), those toward the end (9 months), and those after (12 months). During the learning phase, we measure an oscillatory biomarker of critical period plasticity to determine whether either (or both) learning mechanisms are gated by critical periods. In Set 2, we add visual phonetic cues (talking faces) and in Set 3, oral-motor manipulations, to probe how multisensory information interacts with learning and/or the timing of plasticity. Set 4 asks whether the two learning mechanisms interface equally well with higher levels of language acquisition, by testing whether the reorganized phonetic categories yield commutable phonemes that can be used to distinguish meaningful words. To probe whether plasticity has closed off entirely or can be reopened, in Set 5, we test older children's and adults' performance in these two learning procedures, and in Set 6, we ask whether externally entraining gamma oscillations can reopen plasticity in adults. Together, these studies query the very foundation of what spoken human language entails, the establishment of duality of patterning' how patterning at the level of form (e.g., speech) supports patterning at the level of meaning. To the extent that this foundational achievement is constrained by critical periods in early life and is influenced by the multisensory information inherent in parent-infant enface interactions, we gain deeper insight into the confluence of forces fundamental to the evolution of language. These results will also have important applied implications, both for infants deprived of engaging enface interactions with caregivers (e.g., those who experience extreme early adversity) and for infants born with sensory or motor impairments that limit their experience of multisensory information (e.g., those with visual or oral-motor impairments).