Sequence and Location of Cortical Activity When Infants Understand Words

描述（由申请人提供）：语言是人类经验的核心，但我们对早期发育期间的神经基质知之甚少，因为用于观察婴儿大脑活动的现有技术具有较低的解剖学或时间分辨率，与神经活动有间接关系，需要更多的行为成熟度，或存款电离辐射。相比之下，脑磁图（MEG）是无声的，婴儿耐受性良好。脑磁图直接和即时测量认知信息处理的神经元内电流。我们建议记录全头部306通道脑磁图在文字处理的婴儿。通过将源限制在同一个体的皮层中，从婴儿睡眠时进行的MRI重建，将获得良好的解剖分辨率。我们最初的重点是14个月大的婴儿，他们通常理解几十个单词，这是测试所需的最低限度。然后，我们将这些方法扩展到~18个月大的婴儿，其迅速发展的表达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，以及与每个单词的振幅，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位于经典语言区域的约400 ms的MEG活动。在潜伏期和定位，这种活动类似于N400米诱发的话在成年人。通过测试婴儿N400 m是否与成人N400 m具有关键的认知特征，特别是对重复和语义启动的敏感性，来确认这种同源性。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查。初步数据表明，婴儿N400 m，像成人N400 m，是由语义一致性抑郁。这些研究将建立婴儿由单词引起的神经活动的基本模式，将其与感官反应分离，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，可严重限制心理社会发展。这项研究将开发一种方法来安全地测量婴儿文字处理的大脑活动，用于研究正常和发育中的婴儿语言发展的神经基础。这些方法的未来应用可能包括评估有语言延迟风险的儿童。

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.