Behavioural Science Institute, Radboud University, Postbus 9104, 6500 HE Nijmegen, The Netherlands.
Donders Institute for Brain, Cognition and Behaviour, Radboud University, Max Planck Institute for Psycholinguistics, Nijmegen, The Netherlands.
Neuropsychologia. 2018 Aug;117:454-471. doi: 10.1016/j.neuropsychologia.2018.07.009. Epub 2018 Jul 7.
The aim of the present fMRI study was to investigate whether typical and dyslexic adult readers differed in the neural correlates of audiovisual speech processing. We tested for Blood Oxygen-Level Dependent (BOLD) activity differences between these two groups in a 1-back task, as they processed written (word, illegal consonant strings) and spoken (auditory, visual and audiovisual) stimuli. When processing written stimuli, dyslexic readers showed reduced activity in the supramarginal gyrus, a region suggested to play an important role in phonological processing, but only when they processed strings of consonants, not when they read words. During the speech perception tasks, dyslexic readers were only slower than typical readers in their behavioral responses in the visual speech condition. Additionally, dyslexic readers presented reduced neural activation in the auditory, the visual, and the audiovisual speech conditions. The groups also differed in terms of superadditivity, with dyslexic readers showing decreased neural activation in the regions of interest. An additional analysis focusing on vision-related processing during the audiovisual condition showed diminished activation for the dyslexic readers in a fusiform gyrus cluster. Our results thus suggest that there are differences in audiovisual speech processing between dyslexic and normal readers. These differences might be explained by difficulties in processing the unisensory components of audiovisual speech, more specifically, dyslexic readers may benefit less from visual information during audiovisual speech processing than typical readers. Given that visual speech processing supports the development of phonological skills fundamental in reading, differences in processing of visual speech could contribute to differences in reading ability between typical and dyslexic readers.
本 fMRI 研究旨在探讨典型阅读障碍者和成年阅读障碍者在视听言语处理的神经相关性上是否存在差异。我们在 1 -back 任务中测试了这两组人在处理书面（单词、非法辅音串）和口语（听觉、视觉和视听）刺激时的血氧水平依赖（BOLD）活性差异。在处理书面刺激时，阅读障碍者在处理辅音串时，而非在阅读单词时，其缘上回活动减少，该区域被认为在语音处理中起着重要作用。在言语感知任务中，阅读障碍者仅在视觉言语条件下的行为反应中比典型读者慢。此外，阅读障碍者在听觉、视觉和视听言语条件下的神经激活减少。两组在超加性方面也存在差异，阅读障碍者在感兴趣区域的神经激活减少。一项额外的分析专注于视听条件下与视觉相关的处理，发现阅读障碍者在梭状回簇中的激活减少。因此，我们的研究结果表明，阅读障碍者和正常读者在视听言语处理方面存在差异。这些差异可能是由于处理视听言语的单感觉成分存在困难，更具体地说，阅读障碍者在视听言语处理过程中可能比典型读者从视觉信息中获益更少。鉴于视觉言语处理支持阅读中基本的语音技能的发展，视觉言语处理方面的差异可能导致典型读者和阅读障碍者在阅读能力上的差异。
