Livingstone M S, Rosen G D, Drislane F W, Galaburda A M
Department of Neurobiology, Harvard Medical School, Boston, MA 02115.
Proc Natl Acad Sci U S A. 1991 Sep 15;88(18):7943-7. doi: 10.1073/pnas.88.18.7943.
Several behavioral studies have shown that developmental dyslexics do poorly in tests requiring rapid visual processing. In primates fast, low-contrast visual information is carried by the magnocellular subdivision of the visual pathway, and slow, high-contrast information is carried by the parvocellular division. In this study, we found that dyslexic subjects showed diminished visually evoked potentials to rapid, low-contrast stimuli but normal responses to slow or high-contrast stimuli. The abnormalities in the dyslexic subjects' evoked potentials were consistent with a defect in the magnocellular pathway at the level of visual area 1 or earlier. We then compared the lateral geniculate nuclei from five dyslexic brains to five control brains and found abnormalities in the magnocellular, but not the parvocellular, layers. Studies using auditory and somatosensory tests have shown that dyslexics do poorly in these modalities only when the tests require rapid discriminations. We therefore hypothesize that many cortical systems are similarly divided into a fast and a slow subdivision and that dyslexia specifically affects the fast subdivisions.
多项行为研究表明，发育性阅读障碍患者在需要快速视觉处理的测试中表现不佳。在灵长类动物中，快速、低对比度的视觉信息由视觉通路的大细胞分支传导，而缓慢、高对比度的信息由小细胞分支传导。在本研究中，我们发现阅读障碍受试者对快速、低对比度刺激的视觉诱发电位减弱，但对缓慢或高对比度刺激的反应正常。阅读障碍受试者诱发电位的异常与视觉1区或更早水平的大细胞通路缺陷一致。然后，我们将五个阅读障碍大脑的外侧膝状体核与五个对照大脑进行比较，发现大细胞层而非小细胞层存在异常。使用听觉和体感测试的研究表明，阅读障碍患者只有在测试需要快速辨别时，在这些模式下才表现不佳。因此，我们假设许多皮质系统同样分为快速和慢速两个分支，而阅读障碍 specifically 影响快速分支。
（注：原文中“specifically”翻译为“具体地”不太符合语境，这里推测可能是“specific”拼写错误，按照“specific”翻译为“特定地”，但感觉整体语义不太通顺，若有更准确的原文信息，可进一步完善翻译。）
