Sequence and Location of Cortical Activity When Infants Understand Words

描述(申请人提供)：语言是人类经验的核心，但我们对其早期发育过程中的神经基础知之甚少，因为现有的观察婴儿大脑活动的技术解剖或时间分辨率较低，与神经活动有间接关系，需要更多的行为成熟，或沉积电离辐射。相比之下，脑磁图(MEG)无声，婴儿耐受性好。脑磁图直接和瞬时测量认知信息处理的神经细胞内电流。我们建议记录婴儿在文字处理过程中的全头306通道脑磁图。通过将来源限制在同一个人的皮质中，在婴儿睡着时进行核磁共振重建，将获得良好的解剖学分辨率。我们最初的重点是14个月大的婴儿，他们通常能理解几十个单词，这是测试所需的最低要求。然后，我们将把这些方法扩展到18个月大的婴儿，他们迅速增长的富有表现力的词汇允许大脑反应与语言发展的个体差异相关。在基本任务中，婴儿听他们理解的单词，以及与每个单词的幅度、轮廓和频谱密度相匹配的噪音。在初步数据中，这种比较可靠地唤起了定位于经典语言区域的~400ms的脑磁图活动。在潜伏期和局部化方面，这一活动类似于成人言语诱发的N400m。通过测试婴儿N400m与成人N400m是否具有关键的认知特征，特别是对重复和语义启动的敏感度，将寻求这种同源性的确认。语义启动将通过呈现一幅图片，然后呈现一个与图片匹配或不匹配的听觉单词来检验。初步数据表明，婴儿的N400m和成人的N400m一样，都受到语义重合的抑制。这项拟议的研究将建立一个婴儿由词语引起的神经活动的基本模式，将其与感觉反应分离，并证明其与语义理解的关系。这将有助于揭示用于获得语言理解的神经回路和突触机制，并允许对有语言障碍风险的婴儿进行测量。 公共卫生相关性：语言习得障碍很常见，会严重限制心理社会发展。这项研究将开发一种安全地测量婴儿文字处理背后的大脑活动的方法，用于研究正常和非典型发育婴儿语言发育的神经基础。这些方法的未来应用可能包括评估语言迟缓的高危儿童。

DESCRIPTION (provided by applicant): Language is central to human experience, but we know very little regarding its neural substrate during early development because existing techniques for observing brain activity in infants have low anatomical or temporal resolution, an indirect relationship to neural activity, require more behavioral maturity, or deposit ionizing radiation. In contrast, magnetoencephalography (MEG) is silent and well tolerated by infants. MEG directly and instantaneously measures intraneuronal currents underlying cognitive information processing. We propose to record whole-head 306 channel MEG during word processing by infants. Good anatomical resolution will be obtained by constraining the sources to lie in the cortex of the same individual, reconstructed from MRI performed while the infant is asleep. Our initial focus is on ~14 month old infants, who typically understand a few tens of words, the minimum needed for testing. We will then extend these methods to ~18 month old infants, whose burgeoning expressive vocabularies permit correlation of brain responses with individual differences in language development. In the basic task, infants listen to words they understand, and to noise matched for amplitude, contour and spectral density to each word. In preliminary data, this comparison reliably evokes MEG activity at ~400ms localized to classical language regions. In latency and localization, this activity resembles the N400m evoked by words in adults. Confirmation of this homology will be sought by testing if the infant N400m shares key cognitive characteristics with the adult N400m, specifically sensitivity to repetition and semantic priming. Semantic priming will be examined by presenting a picture and then an auditory word which either matches the picture or not. Preliminary data indicates that the infant N400m, like the adult N400m, is depressed by semantic congruence. The proposed studies will establish a basic pattern of neural activity evoked by words in infants, dissociate it from sensory responses, and demonstrate its relationship to semantic understanding. This would help reveal the neural circuits and synaptic mechanisms used to acquire language understanding, and allow their measurement in infants at risk for language disorders. PUBLIC HEALTH RELEVANCE: Disorders of language acquisition are common and can severely limit psychosocial development. This research will develop a method to safely measure the brain activity underlying infant word-processing, to be used to study the neural basis of language development in both normal and atypically developing infants. Future applications of these methods may include the assessment of children at-risk for delayed language.