Yong Keir X X, Shakespeare Timothy J, Cash Dave, Henley Susie M D, Warren Jason D, Crutch Sebastian J
Dementia Research Centre, Department of Neurodegeneration, UCL Institute of Neurology, University College London, London, UK.
Dementia Research Centre, Department of Neurodegeneration, UCL Institute of Neurology, University College London, London, UK.
Cortex. 2014 Aug;57:92-106. doi: 10.1016/j.cortex.2014.03.010. Epub 2014 Apr 12.
Reading deficits are a common early feature of the degenerative syndrome posterior cortical atrophy (PCA) but are poorly understood even at the single word level. The current study evaluated the reading accuracy and speed of 26 PCA patients, 17 typical Alzheimer's disease (tAD) patients and 14 healthy controls on a corpus of 192 single words in which the following perceptual properties were manipulated systematically: inter-letter spacing, font size, length, font type, case and confusability. PCA reading was significantly less accurate and slower than tAD patients and controls, with performance significantly adversely affected by increased letter spacing, size, length and font (cursive < non-cursive), and characterised by visual errors (69% of all error responses). By contrast, tAD and control accuracy rates were at or near ceiling, letter spacing was the only perceptual factor to influence reading speed in the same direction as controls, and, in contrast to PCA patients, control reading was faster for larger font sizes. The inverse size effect in PCA (less accurate reading of large than small font size print) was associated with lower grey matter volume in the right superior parietal lobule. Reading accuracy was associated with impairments of early visual (especially crowding), visuoperceptual and visuospatial processes. However, these deficits were not causally related to a universal impairment of reading as some patients showed preserved reading for small, unspaced words despite grave visual deficits. Rather, the impact of specific types of visual dysfunction on reading was found to be (con)text specific, being particularly evident for large, spaced, lengthy words. These findings improve the characterisation of dyslexia in PCA, shed light on the causative and associative factors, and provide clear direction for the development of reading aids and strategies to maximise and sustain reading ability in the early stages of disease.
阅读缺陷是退行性综合征——后皮质萎缩（PCA）常见的早期特征，但即使在单个单词层面也未被充分理解。本研究评估了26名PCA患者、17名典型阿尔茨海默病（tAD）患者和14名健康对照者对192个单词语料库的阅读准确性和速度，其中对以下感知属性进行了系统操纵：字母间距、字体大小、长度、字体类型、大小写和易混淆性。PCA患者的阅读准确性明显低于tAD患者和对照组，速度也较慢，字母间距增加、大小、长度和字体（草书＜非草书）的增加会显著影响其表现，且以视觉错误为特征（占所有错误反应的69%）。相比之下，tAD患者和对照组的准确率达到或接近上限，字母间距是唯一与对照组在相同方向上影响阅读速度的感知因素，与PCA患者不同的是，对照组对较大字体的阅读速度更快。PCA中的逆大小效应（大字体印刷的阅读准确性低于小字体）与右侧顶上小叶灰质体积较低有关。阅读准确性与早期视觉（尤其是拥挤效应）、视觉感知和视觉空间过程的损伤有关。然而，这些缺陷并非与普遍的阅读障碍有因果关系，因为一些患者尽管存在严重的视觉缺陷，但对小的、无间距的单词仍表现出保留的阅读能力。相反，特定类型的视觉功能障碍对阅读的影响是（与）上下文相关的，在大的、有间距的、长单词中尤为明显。这些发现改善了PCA中诵读困难的特征描述，阐明了因果和关联因素，并为开发阅读辅助工具和策略提供了明确方向，以在疾病早期最大化并维持阅读能力。
