汉语发展性阅读障碍儿童的视觉大细胞通路特点

Developmental dyslexia (DD) is a common kind of learning disorder, which affects 5-18% of people. It seems important to explore the deficit in visual magnocellular pathway in Chinese developmental dyslexia, for many researches demonstrated that one of the core deficits of Chinese developmental dyslexia was orthographic deficit which was associated with the deficit in visual magnocellular pathway. Two studies were done to detect the differences among Chinese developmental dyslexics, average readers of the same chronological age (CA controls) and average readers of the same reading level (RL controls) in reaction time, accuracy and visual mismatch negativity (vMMN) elicited by the moving gratings responded by visual magnocellular pathway. There were two grating-conditions which were low contrast/low spatial frequency condition and high contrast/high spatial frequency condition respectively. In ERP study, a modified “cross-modal delayed response” paradigm was used to elicit the vMMN. The results showed that the developmental dyslexics responded slower than CA controls, had more errors than RL controls, and had smaller amplitudes of vMMNs than the two controls in visual magnocellular pathway condition, but not in control condition. That is to say, Chinese developmental dyslexics had deficits in visual magnocellular pathway.

发展性阅读障碍（Developmental dyslexia，DD）是一种常见的学习障碍。与拼音文字发展性阅读障碍的核心缺陷是语音缺陷的结论不同，汉语发展性阅读障碍的主要缺陷之一是正字法加工技能缺陷，而正字法加工技能与视觉大细胞通路有显著相关，所以探索汉语发展性阅读障碍的视觉大细胞通路特点显得尤为重要。本研究从行为方面和脑神经方面对汉语DD者进行视觉大细胞通路特点的探索。在行为方面，本研究采用反应时和正确率作为指标研究发展性阅读障碍组儿童、同年龄对照组儿童和同阅读水平对照组儿童视觉大细胞通路的特点。在脑神经方面，利用视觉失匹配负波（visual mismatch negativity , vMMN）探索发展性阅读障碍组儿童与同年龄对照组儿童和同阅读水平对照组儿童对视觉大细胞通路的敏感性。视觉刺激分为视觉大细胞通路条件（低对比度、低空间频率光栅）和对比条件（高对比度、高空间频率光栅）。研究结果为：行为研究中，在视觉大细胞通路条件下，DD组的反应时比同年龄对照组儿童显著延长，虽然DD组与同阅读水平对照组在反应时上没有差异，但是DD组表现出更多的错误。在ERP研究中，在视觉大细胞通路条件下，发展性阅读障碍组的vMMN波幅显著低于同年龄对照组和同阅读水平对照组，而在对比条件下，发展性阅读障碍组儿童与两个对照组儿童的vMMN波幅没有显著差异。这些结果表明汉语发展性阅读障碍儿童存在视觉大细胞通路缺陷。而且，相关分析发现正字法加工技能测验与视觉大细胞通路条件下的vMMN波幅相关显著。