Lau Joseph C Y, Wong Patrick C M, Chandrasekaran Bharath
Department of Linguistics and Modern Languages, The Chinese University of Hong Kong, Shatin, Hong Kong.
Brain and Mind Institute, The Chinese University of Hong Kong, Shatin, Hong Kong.
J Neurophysiol. 2017 Feb 1;117(2):594-603. doi: 10.1152/jn.00656.2016. Epub 2016 Nov 9.
We examined the mechanics of online experience-dependent auditory plasticity by assessing the influence of prior context on the frequency-following responses (FFRs), which reflect phase-locked responses from neural ensembles within the subcortical auditory system. FFRs were elicited to a Cantonese falling lexical pitch pattern from 24 native speakers of Cantonese in a variable context, wherein the falling pitch pattern randomly occurred in the context of two other linguistic pitch patterns; in a patterned context, wherein, the falling pitch pattern was presented in a predictable sequence along with two other pitch patterns, and in a repetitive context, wherein the falling pitch pattern was presented with 100% probability. We found that neural tracking of the stimulus pitch contour was most faithful and accurate when listening context was patterned and least faithful when the listening context was variable. The patterned context elicited more robust pitch tracking relative to the repetitive context, suggesting that context-dependent plasticity is most robust when the context is predictable but not repetitive. Our study demonstrates a robust influence of prior listening context that works to enhance online neural encoding of linguistic pitch patterns. We interpret these results as indicative of an interplay between contextual processes that are responsive to predictability as well as novelty in the presentation context.
NEW & NOTEWORTHY: Human auditory perception in dynamic listening environments requires fine-tuning of sensory signal based on behaviorally relevant regularities in listening context, i.e., online experience-dependent plasticity. Our finding suggests what partly underlie online experience-dependent plasticity are interplaying contextual processes in the subcortical auditory system that are responsive to predictability as well as novelty in listening context. These findings add to the literature that looks to establish the neurophysiological bases of auditory system plasticity, a central issue in auditory neuroscience.
我们通过评估先前语境对频率跟随反应（FFR）的影响，研究了在线经验依赖性听觉可塑性的机制，FFR反映了皮质下听觉系统中神经集合的锁相反应。对24名以粤语为母语的人在可变语境中呈现粤语降调词汇音高模式来诱发FFR，其中降调模式随机出现在另外两种语言音高模式的语境中；在有模式的语境中，降调模式与另外两种音高模式按可预测顺序呈现；在重复语境中，降调模式以100%的概率呈现。我们发现，当听觉语境有模式时，对刺激音高轮廓的神经跟踪最准确可靠，而当听觉语境可变时则最不可靠。与重复语境相比，有模式的语境诱发了更强健的音高跟踪，这表明当语境可预测但不重复时，语境依赖性可塑性最强。我们的研究证明了先前听觉语境的强大影响，这种影响有助于增强对语言音高模式的在线神经编码。我们将这些结果解释为对可预测性以及呈现语境中的新颖性做出反应的语境过程之间相互作用的表现。
在动态听觉环境中的人类听觉感知需要根据听觉语境中与行为相关的规律对感觉信号进行微调，即在线经验依赖性可塑性。我们的发现表明，在线经验依赖性可塑性的部分基础是皮质下听觉系统中相互作用的语境过程，这些过程对听觉语境中的可预测性和新颖性都有反应。这些发现为旨在建立听觉系统可塑性神经生理学基础的文献增添了内容，这是听觉神经科学中的一个核心问题。
