Power Alan James, Mead Natasha, Barnes Lisa, Goswami Usha
Department of Experimental Psychology, Centre for Neuroscience in Education, University of Cambridge Cambridge, UK.
Front Psychol. 2012 Jul 19;3:216. doi: 10.3389/fpsyg.2012.00216. eCollection 2012.
Auditory cortical oscillations have been proposed to play an important role in speech perception. It is suggested that the brain may take temporal "samples" of information from the speech stream at different rates, phase resetting ongoing oscillations so that they are aligned with similar frequency bands in the input ("phase locking"). Information from these frequency bands is then bound together for speech perception. To date, there are no explorations of neural phase locking and entrainment to speech input in children. However, it is clear from studies of language acquisition that infants use both visual speech information and auditory speech information in learning. In order to study neural entrainment to speech in typically developing children, we use a rhythmic entrainment paradigm (underlying 2 Hz or delta rate) based on repetition of the syllable "ba," presented in either the auditory modality alone, the visual modality alone, or as auditory-visual speech (via a "talking head"). To ensure attention to the task, children aged 13 years were asked to press a button as fast as possible when the "ba" stimulus violated the rhythm for each stream type. Rhythmic violation depended on delaying the occurrence of a "ba" in the isochronous stream. Neural entrainment was demonstrated for all stream types, and individual differences in standardized measures of language processing were related to auditory entrainment at the theta rate. Further, there was significant modulation of the preferred phase of auditory entrainment in the theta band when visual speech cues were present, indicating cross-modal phase resetting. The rhythmic entrainment paradigm developed here offers a method for exploring individual differences in oscillatory phase locking during development. In particular, a method for assessing neural entrainment and cross-modal phase resetting would be useful for exploring developmental learning difficulties thought to involve temporal sampling, such as dyslexia.
听觉皮层振荡被认为在言语感知中起重要作用。有人提出，大脑可能以不同速率从言语流中提取时间“样本”，重置正在进行的振荡的相位，使其与输入中的相似频段对齐（“相位锁定”）。然后，来自这些频段的信息被整合在一起用于言语感知。迄今为止，尚未对儿童中神经相位锁定和对言语输入的同步化进行探索。然而，从语言习得研究中可以清楚地看出，婴儿在学习过程中同时使用视觉言语信息和听觉言语信息。为了研究正常发育儿童对言语的神经同步化，我们使用了一种基于音节“ba”重复的节律同步范式（以2赫兹或δ波频率为基础），该范式以单独的听觉模态、单独的视觉模态或视听言语（通过“会说话的头像”）呈现。为确保儿童专注于任务，要求13岁的儿童在每种流类型的“ba”刺激违反节律时尽快按下按钮。节律违反取决于在等时流中延迟“ba”的出现。所有流类型均显示出神经同步化，并且语言处理标准化测量中的个体差异与θ波频率下的听觉同步化有关。此外，当存在视觉言语线索时，θ频段听觉同步化的偏好相位有显著调制，表明跨模态相位重置。这里开发的节律同步范式提供了一种探索发育过程中振荡相位锁定个体差异的方法。特别是，一种评估神经同步化和跨模态相位重置的方法对于探索被认为涉及时间采样的发育性学习困难（如诵读困难）将是有用的。
