Eden G F, VanMeter J W, Rumsey J M, Maisog J M, Woods R P, Zeffiro T A
Section on Functional Brain Imaging NIMH, National Institutes of Health, Bethesda, Maryland 20892, USA.
Nature. 1996 Jul 4;382(6586):66-9. doi: 10.1038/382066a0.
It is widely accepted that dyslexics have deficits in reading and phonological awareness, but there is increasing evidence that they also exhibit visual processing abnormalities that may be confined to particular portions of the visual system. In primate visual pathways, inputs from parvocellular or magnocellular layers of the lateral geniculate nucleus remain partly segregated in projections to extrastriate cortical areas specialized for processing colour and form versus motion. In studies of dyslexia, psychophysical and anatomical evidence indicate an anomaly in the magnocellular visual subsystem. To investigate the pathophysiology of dyslexia, we used functional magnetic resonance imaging (fMRI) to study visual motion processing in normal and dyslexic men. In all dyslexics, presentation of moving stimuli failed to produce the same task-related functional activation in area V5/MT (part of the magnocellular visual subsystem) observed in controls. In contrast, presentation of stationary patterns resulted in equivalent activations in V1/V2 and extrastriate cortex in both groups. Although previous studies have emphasized language deficits, our data reveal differences in the regional functional organization of the cortical visual system in dyslexia.
人们普遍认为，诵读困难症患者在阅读和语音意识方面存在缺陷，但越来越多的证据表明，他们还表现出视觉处理异常，这种异常可能局限于视觉系统的特定部分。在灵长类动物的视觉通路中，外侧膝状体核小细胞层或大细胞层的输入在投射到专门处理颜色和形状与运动的纹外皮层区域时仍部分分离。在诵读困难症的研究中，心理物理学和解剖学证据表明大细胞视觉子系统存在异常。为了研究诵读困难症的病理生理学，我们使用功能磁共振成像（fMRI）来研究正常男性和诵读困难男性的视觉运动处理。在所有诵读困难症患者中，呈现移动刺激未能在V5/MT区域（大细胞视觉子系统的一部分）产生与对照组中观察到的相同的任务相关功能激活。相比之下，呈现静止图案在两组的V1/V2和纹外皮层中导致了等效的激活。尽管先前的研究强调了语言缺陷，但我们的数据揭示了诵读困难症患者皮层视觉系统区域功能组织的差异。
