Zhang Yisi S, Ghazanfar Asif A
Princeton Neuroscience Institute, Princeton University, Princeton, NJ 08544, USA; Department of Psychology, Princeton University, Princeton, NJ 08544, USA.
Princeton Neuroscience Institute, Princeton University, Princeton, NJ 08544, USA; Department of Psychology, Princeton University, Princeton, NJ 08544, USA.
Curr Biol. 2016 May 23;26(10):1249-60. doi: 10.1016/j.cub.2016.03.023. Epub 2016 Apr 7.
The variable vocal behavior of human infants is the scaffolding upon which speech and social interactions develop. It is important to know what factors drive this developmentally critical behavioral output. Using marmoset monkeys as a model system, we first addressed whether the initial conditions for vocal output and its sequential structure are perinatally influenced. Using dizygotic twins and Markov analyses of their vocal sequences, we found that in the first postnatal week, twins had more similar vocal sequences to each other than to their non-twin siblings. Moreover, both twins and their siblings had more vocal sequence similarity with each other than with non-sibling infants. Using electromyography, we then investigated the physiological basis of vocal sequence structure by measuring respiration and arousal levels (via changes in heart rate). We tested the hypothesis that early-life influences on vocal output are via fluctuations of the autonomic nervous system (ANS) mediated by vocal biomechanics. We found that arousal levels fluctuate at ∼0.1 Hz (the Mayer wave) and that this slow oscillation modulates the amplitude of the faster, ∼1.0 Hz respiratory rhythm. The systematic changes in respiratory amplitude result in the different vocalizations that comprise infant vocal sequences. Among twins, the temporal structure of arousal level changes was similar and therefore indicates why their vocal sequences were similar. Our study shows that vocal sequences are tightly linked to respiratory patterns that are modulated by ANS fluctuations and that the temporal structure of ANS fluctuations is perinatally influenced.
人类婴儿多变的发声行为是言语和社会互动发展的基础。了解哪些因素驱动这种对发育至关重要的行为输出很重要。我们以狨猴作为模型系统，首先探讨了发声输出的初始条件及其序列结构是否在围产期受到影响。通过对异卵双胞胎及其发声序列进行马尔可夫分析，我们发现，在出生后的第一周，双胞胎之间的发声序列比他们与非双胞胎兄弟姐妹的发声序列更为相似。此外，双胞胎及其兄弟姐妹之间的发声序列相似性高于他们与非兄弟姐妹婴儿之间的相似性。然后，我们使用肌电图，通过测量呼吸和唤醒水平（通过心率变化）来研究发声序列结构的生理基础。我们检验了这样一个假设，即生命早期对发声输出的影响是通过由发声生物力学介导的自主神经系统（ANS）的波动实现的。我们发现，唤醒水平以约0.1赫兹（迈尔波）的频率波动，这种缓慢的振荡调节了更快的、约1.0赫兹的呼吸节律的幅度。呼吸幅度的系统性变化导致了构成婴儿发声序列的不同发声。在双胞胎中，唤醒水平变化的时间结构是相似的，因此说明了他们的发声序列为何相似。我们的研究表明，发声序列与由ANS波动调节的呼吸模式紧密相连，并且ANS波动的时间结构在围产期受到影响。
