Department of Optometry and Vision Sciences, The University of Melbourne, Parkville, Victoria, Australia.
Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, Victoria, Australia.
Neuropsychologia. 2021 May 14;155:107819. doi: 10.1016/j.neuropsychologia.2021.107819. Epub 2021 Mar 5.
Dyslexia is characterised by poor reading ability. Its aetiology is probably multifactorial, with abnormal visual processing playing an important role. Among adults with normal reading ability, there is a larger representation of central visual field in the primary visual cortex (V1) in those with more efficient visuospatial attention. In this study, we tested the hypothesis that poor reading ability in school-aged children (17 children with dyslexia, 14 control children with normal reading ability) is associated with deficits in visuospatial attention using a visual search task. We corroborated the psychophysical findings with neuroimaging, by measuring the functional size of V1 in response to a central 12° visual stimulus. Consistent with other literature, visual search was impaired and less efficient in the dyslexic children, particularly with more distractor elements in the search array (p = 0.04). We also found atypical interhemispheric asymmetry in functional V1 size in the dyslexia group (p = 0.02). Reading impaired children showed poorer visual search efficiency (p = 0.01), needing more time per unit distractor (higher ms/item). Reading ability was also correlated with V1 size asymmetry (p = 0.03), such that poorer readers showed less left hemisphere bias relative to the right hemisphere. Our findings support the view that dyslexic children have abnormal visuospatial attention and interhemispheric V1 asymmetry, relative to chronological age-matched peers, and that these factors may contribute to inter-individual variation in reading performance in children.
阅读障碍的特点是阅读能力差。其病因可能是多因素的，异常的视觉处理起着重要作用。在阅读能力正常的成年人中，在具有更高效的视空间注意力的人中，初级视觉皮层（V1）中的中央视觉区域有更大的代表性。在这项研究中，我们使用视觉搜索任务测试了一个假设，即学龄儿童（17 名阅读障碍儿童，14 名阅读能力正常的对照儿童）的阅读能力差与视空间注意力缺陷有关。我们通过测量对中央 12°视觉刺激的 V1 的功能大小，用神经影像学方法证实了心理物理学发现。与其他文献一致，阅读障碍儿童的视觉搜索受到损害且效率较低，尤其是在搜索数组中有更多干扰元素时（p=0.04）。我们还发现阅读障碍组的功能性 V1 大小存在异常的左右半球不对称（p=0.02）。阅读障碍儿童的视觉搜索效率较差（p=0.01），每个干扰物需要更多的时间（ms/item 更高）。阅读能力也与 V1 大小不对称相关（p=0.03），即阅读能力较差的儿童相对于右半球，左半球的偏侧性较小。我们的发现支持这样一种观点，即阅读障碍儿童的视空间注意力和左右半球 V1 不对称异常，与年龄匹配的同龄人相比，这些因素可能导致儿童阅读表现的个体差异。
