Cognitive Brain Research Unit, Department of Psychology and Logopedics, Faculty of Medicine, University of Helsinki, Finland.
Department of Neuroscience and Biomedical Engineering, School of Science, Aalto University, Finland.
Neuroimage. 2020 Aug 1;216:116799. doi: 10.1016/j.neuroimage.2020.116799. Epub 2020 Apr 12.
Listening to speech elicits brain activity time-locked to the speech sounds. This so-called neural entrainment to speech was found to be atypical in dyslexia, a reading impairment associated with neural speech processing deficits. We hypothesized that the brain responses of dyslexic vs. normal readers to real-life speech would be different, and thus the strength of inter-subject correlation (ISC) would differ from that of typical readers and be reflected in reading-related measures. We recorded magnetoencephalograms (MEG) of 23 dyslexic and 21 typically-reading adults during listening to ~10 min of natural Finnish speech consisting of excerpts from radio news, a podcast, a self-recorded audiobook chapter and small talk. The amplitude envelopes of band-pass-filtered MEG source signals were correlated between subjects in a cortically-constrained source space in six frequency bands. The resulting ISCs of dyslexic and typical readers were compared with a permutation-based t-test. Neuropsychological measures of phonological processing, technical reading, and working memory were correlated with the ISCs utilizing the Mantel test. During listening to speech, ISCs were mainly reduced in dyslexic compared to typical readers in delta (0.5-4 Hz) and high gamma (55-90 Hz) frequency bands. In the theta (4-8 Hz), beta (12-25 Hz), and low gamma (25-45 Hz) bands, dyslexics had enhanced ISCs to speech compared to controls. Furthermore, we found that ISCs across both groups were associated with phonological processing, technical reading, and working memory. The atypical ISCs to natural speech in dyslexics supports the temporal sampling deficit theory of dyslexia. It also suggests over-synchronization to phoneme-rate information in speech, which could indicate more effort-demanding sampling of phonemes from speech in dyslexia. These irregularities in parsing speech are likely some of the complex neural factors contributing to dyslexia. The associations between neural coupling and reading-related skills further support this notion.
听言语会引发与言语声音时间锁相的大脑活动。这种所谓的神经与言语的同步化在阅读障碍中是异常的，阅读障碍是一种与神经言语处理缺陷相关的阅读障碍。我们假设，与正常读者相比，阅读障碍者对真实言语的大脑反应会有所不同，因此，受试者之间的相关性（ISC）强度会与典型读者不同，并反映在与阅读相关的测量中。我们记录了 23 名阅读障碍者和 21 名正常阅读者在听约 10 分钟的自然芬兰语时的脑磁图（MEG），这些言语由广播新闻、播客、自我录制的有声读物章节和闲聊的摘录组成。在六个频带的皮质约束源空间中，对带通滤波的 MEG 源信号的振幅包络进行了受试者间的相关性分析。利用置换检验比较了阅读障碍者和典型读者的 ISC。利用 Mantel 检验，将语音处理、技术阅读和工作记忆的神经心理学测量与 ISC 相关联。在听言语时，与典型读者相比，阅读障碍者在 delta（0.5-4 Hz）和高 gamma（55-90 Hz）频段的 ISC 主要降低。在 theta（4-8 Hz）、beta（12-25 Hz）和低 gamma（25-45 Hz）频段，阅读障碍者的 ISC 比对照组更强。此外，我们发现两组的 ISC 都与语音处理、技术阅读和工作记忆有关。阅读障碍者对自然言语的非典型 ISC 支持阅读障碍的时间采样缺陷理论。它还表明对言语中音素率信息的过度同步，这可能表明在阅读障碍中，从言语中抽样音素需要更多的努力。这些言语解析的不规则性可能是导致阅读障碍的一些复杂神经因素之一。神经耦合与阅读相关技能之间的关联进一步支持了这一观点。
