Centro de Investigação Interdisciplinar em Saúde (CIIS), Universidade Católica Portuguesa, Palma de Cima, Lisboa, Portugal.
Centre for Neuroscience in Education, Department of Psychology, University of Cambridge, Cambridge, United Kingdom.
PLoS One. 2018 Oct 24;13(10):e0205224. doi: 10.1371/journal.pone.0205224. eCollection 2018.
The temporal modulation structure of speech plays a key role in neural encoding of the speech signal. Amplitude modulations (AMs, quasi-rhythmic changes in signal energy or intensity) in speech are encoded by neuronal oscillations (rhythmic variations in neural excitability in large cell networks) that oscillate at matching temporal rates. To date, however, all neural studies have investigated adult-directed speech (ADS) as produced and perceived by highly literate adults. Whether temporal features of ADS vary with the skills of the speaker, for example literacy skills, is currently unknown. Here we analyse the temporal structure of ADS spoken by illiterate, low literate (≤ 4 years of literacy) and highly literate (≥ 12 years of literacy) adults. We find that illiterates produce speech differently. Spontaneous conversational speech produced by illiterate adults showed significantly less synchronised coupling between AM bands (less phase synchronisation) than conversational speech produced by low literate and highly literate adults, and contained significantly fewer syllables per second. There was also a significant relationship between years of literacy and the amount of theta-band energy in conversational speech. When asked to produce rhythmic proverbs learned in childhood, all groups could produce speech with similar AM phase synchronisation, suggesting that the differences in spontaneous conversational speech were not caused by physiological constraints. The data suggest that the temporal modulation structure of spoken language changes with the acquisition of cultural skills like literacy that are usually a product of schooling. There is a cultural effect on the temporal modulation structure of spoken language.
语音的时调制结构在语音信号的神经编码中起着关键作用。语音中的幅度调制（AMs，信号能量或强度的准周期性变化）是由神经元振荡（大细胞网络中神经兴奋性的节律变化）编码的，这些振荡以匹配的时间速率发生。然而，迄今为止，所有的神经研究都调查了成人导向的语音（ADS），这些语音是由受过高度教育的成年人产生和感知的。目前尚不清楚 ADS 的时间特征是否会随着说话者的技能（例如读写能力）而变化。在这里，我们分析了文盲、低文化程度（≤4 年读写能力）和高文化程度（≥12 年读写能力）成年人所说的 ADS 的时间结构。我们发现文盲的发音方式不同。文盲成年人自发的会话语音表现出 AM 频带之间的同步耦合（相位同步减少）明显少于低文化程度和高文化程度成年人的会话语音，并且每秒包含的音节明显较少。读写能力的年数与会话语音中的 theta 频带能量之间也存在显著关系。当被要求说出儿时学过的有节奏的谚语时，所有组都可以用类似的 AM 相位同步产生语音，这表明自发会话语音中的差异不是由生理限制引起的。这些数据表明，口语的时间调制结构随着文化技能（如读写能力）的获得而变化，而这些技能通常是学校教育的产物。口语的时间调制结构存在文化影响。
