Human neonates can discriminate phonemes, but the neural mechanism underlying this ability is poorly understood. Here we show that the neonatal brain can learn to discriminate natural vowels from backward vowels, a contrast unlikely to have been learnt in the womb. Using functional near-infrared spectroscopy, we examined the neuroplastic changes caused by 5 h of postnatal exposure to random sequences of natural and reversed (backward) vowels (T1), and again 2 h later (T2). Neonates in the experimental group were trained with the same stimuli as those used at T1 and T2. Compared with controls, infants in the experimental group showed shorter haemodynamic response latencies for forward vs backward vowels at T1, maximally over the inferior frontal region. At T2, neural activity differentially increased, maximally over superior temporal regions and the left inferior parietal region. Neonates thus exhibit ultra-fast tuning to natural phonemes in the first hours after birth.

人类新生儿可以区分音素，但这种能力背后的神经机制却知之甚少。在这里，我们表明新生儿大脑可以学会区分自然元音和后向元音，这是在子宫中不太可能学会的对比。使用功能性近红外光谱，我们检查了产后 5 小时暴露于自然和反向（向后）元音的随机序列 (T1) 和 2 小时后 (T2) 引起的神经塑性变化。实验组的新生儿接受了与 T1 和 T2 相同的刺激训练。与对照组相比，实验组婴儿在 T1 时前向元音和后向元音的血流动力学反应潜伏期更短，最大程度超过额下区域。在 T2 时，神经活动不同程度地增加，最大程度超过上颞区和左下顶叶区。因此，新生儿在出生后的最初几个小时内表现出对自然音素的超快调谐。