Predictive coding in typical speech perception and dyslexia

项目总结/摘要 最常见和最好理解的阅读困难的原因，定义为阅读障碍是一个改变， 对口语的处理。虽然有报道称， 几十年来，一个新兴的文献描述了行为缺陷，依赖于在开发的 感觉环境，以及减少神经适应一致的刺激。因为高效的演讲 处理依赖于特定声音的声学特征的快速可塑性， 受上下文限制的预测，听觉皮层层次中的快速可塑性损伤是一个候选者 阅读障碍的核心缺陷在这里，我们探讨是否减少可塑性由于短期的经验和/或顶部- 低期望值是阅读障碍患者言语知觉的特征。通过记录脑磁图（MEG） 当个体听成对的单词时，我们将确定可预测性如何不同地调节神经元的活动。 阅读障碍的反应。目的1是描述听觉重复抑制的时空模式 阅读障碍的缺陷。目前还不清楚神经适应能力的降低是由于自下而上还是自上而下 机制等我们将评估自下而上的重复抑制，通过测量对语音的反应， 在这些刺激中，单词、声音或两者都被意外地重复，以高时空细节揭示 神经群体如何编码这些特征。减弱的重复抑制表明听觉 系统变化较少，由于短期的经验，文字形式和声音，这可能是一个核心 阅读障碍的神经生物学差异。目标2是描述期望抑制和预测误差 在阅读障碍中的语言缺陷。我们将评估自上而下的期望抑制，通过测量的反应， 成对的言语刺激，其中听者对刺激的重复有很高的期望。一致的 预测编码帐户，我们预计，实现的期望将产生很少的反应，而违反 预期将引起大的预测误差响应，表明需要更新预测。在诵读困难症中， 这些现象中的异常表明对语音学和/或单词音位学的预测不足， 这意味着更高层次的赤字。目标3是对预期刺激出现的探索性量化 神经信号的特征编码我们将训练一个神经模式分类器来区分单词和声音， MEG数据，调查特征是否在预测时出现得更早，更稳健， 不可预测的，正如自上而下的影响所解释的那样。我们将研究个体差异是否 分类器的准确性与神经预测误差的大小和语言能力有关。这些 目的是促进对可能导致阅读障碍的语音处理差异的机械理解。 由于短期经验和/或言语特征预测不足而导致的可塑性降低可能会阻止 大脑从建立和更新的语音-音位关系模型，儿童的基础， 语音意识，声音到印刷品的映射，以及最终的阅读。

PROJECT SUMMARY/ABSTRACT The most common and best understood cause of the reading difficulty that defines dyslexia is an alteration in the processing of spoken language. While speech perception deficits in dyslexia have been reported for decades, a burgeoning literature describes behavioral deficits that rely on the exploitation of regularities in the sensory environment, as well as reduced neural adaptation to consistent stimulation. Because efficient speech processing relies on rapid plasticity for acoustic features characteristic of particular voices, coupled to semantic predictions constrained by context, a rapid plasticity impairment in the auditory cortical hierarchy is a candidate core deficit in dyslexia. Here we explore whether reduced plasticity due to short-term experience and/or top- down expectation characterizes speech perception in dyslexia. By recording magnetoencephalography (MEG) while individuals listen to pairs of words, we will determine how predictability differentially modulates neural responses in dyslexia. Aim 1 is to characterize the spatiotemporal patterns of auditory repetition suppression deficits in dyslexia. It is not known whether reduced neural adaptation is due to bottom-up or top-down mechanisms. We will assess bottom-up repetition suppression by measuring responses to pairs of speech stimuli in which the word, voice, or both are repeated unexpectedly, revealing with high spatiotemporal detail how neural populations encode these features. Attenuated repetition suppression suggests that the auditory system changes less due to short-term experience with word forms and voices, which may be a core neurobiological difference in dyslexia. Aim 2 is to characterize expectation suppression and prediction error deficits for speech in dyslexia. We will assess top-down expectation suppression by measuring responses to pairs of speech stimuli in which listeners have high expectation that stimuli will repeat. Consistent with a predictive coding account, we expect that fulfilled expectations will generate little response, while violated expectations will evoke large prediction error responses, signaling a need to update the prediction. In dyslexia, abnormalities in these phenomena suggest inadequate prediction of voice phonetics and/or word phonology, implicating a higher-order deficit. Aim 3 is an exploratory quantification of the emergence of expected stimulus feature encoding in neural signals. We will train a neural pattern classifier to distinguish words and voices from the MEG data, investigating whether features emerge earlier and more robustly when they are predicted vs. unpredicted, as would be explained by top-down influences. We will investigate whether individual differences in classifier accuracy correlate with the magnitude of neural prediction error and with language abilities. These aims advance a mechanistic understanding of speech processing differences that can lead to dyslexia. Reduced plasticity due to short-term experience and/or inadequate prediction of speech features may prevent the brain from building and updating models of phonetic-phonological relationships that underlie children's phonological awareness, sound-to-print mapping, and, ultimately, reading.