Cognitive Brain Research Unit, Department of Psychology and Logopedics, Faculty of Medicine, University of Helsinki, Haartmaninkatu 3 B, P.O. Box 21, 00014, Helsinki, Finland.
Department of Neurosciences, Faculty of Medicine, University of Helsinki, Helsinki, Finland.
Sci Rep. 2021 May 25;11(1):10862. doi: 10.1038/s41598-021-89317-x.
Developmental dyslexia (DD) is the most prevalent neurodevelopmental disorder with a substantial negative influence on the individual's academic achievement and career. Research on its neuroanatomical origins has continued for half a century, yielding, however, inconsistent results, lowered total brain volume being the most consistent finding. We set out to evaluate the grey matter (GM) volume and cortical abnormalities in adult dyslexic individuals, employing a combination of whole-brain voxel- and surface-based morphometry following current recommendations on analysis approaches, coupled with rigorous neuropsychological testing. Whilst controlling for age, sex, total intracranial volume, and performance IQ, we found both decreased GM volume and cortical thickness in the left insula in participants with DD. Moreover, they had decreased GM volume in left superior temporal gyrus, putamen, globus pallidus, and parahippocampal gyrus. Higher GM volumes and cortical thickness in these areas correlated with better reading and phonological skills, deficits of which are pivotal to DD. Crucially, total brain volume did not influence our results, since it did not differ between the groups. Our findings demonstrating abnormalities in brain areas in individuals with DD, which previously were associated with phonological processing, are compatible with the leading hypotheses on the neurocognitive origins of DD.
发展性阅读障碍（DD）是最常见的神经发育障碍之一，对个体的学业成绩和职业发展有很大的负面影响。对其神经解剖学起源的研究已经持续了半个世纪，但结果并不一致，总脑容量降低是最一致的发现。我们采用了当前推荐的分析方法，结合严格的神经心理学测试，运用全脑体素和皮质表面形态计量学，对成年阅读障碍个体的灰质（GM）体积和皮质异常进行了评估。在控制年龄、性别、总颅内体积和表现智商的情况下，我们发现 DD 患者的左侧脑岛的 GM 体积和皮质厚度都降低了。此外，他们左侧颞上回、壳核、苍白球和海马旁回的 GM 体积也减少了。这些区域的 GM 体积和皮质厚度增加与更好的阅读和语音技能相关，而这些缺陷是 DD 的关键。至关重要的是，由于两组之间的总脑容量没有差异，所以总脑容量并没有影响我们的结果。我们的研究结果表明，DD 患者的大脑区域存在异常，这些区域以前与语音处理有关，这与 DD 的神经认知起源的主要假说相吻合。
