Department of Neurology, Institute of Memory and of Alzheimer's Disease, National Reference Center for "PPA and Rare Dementias", Pitié-Salpêtrière Hospital, AP-HP, Paris, France; Brain and Spine Institute (ICM), ICM-INSERM 1127, FrontLab, Paris, France.
Brain and Spine Institute (ICM), ICM-INSERM 1127, FrontLab, Paris, France.
Neuropsychologia. 2019 Dec;135:107241. doi: 10.1016/j.neuropsychologia.2019.107241. Epub 2019 Nov 1.
The semantic variant of primary progressive aphasia (sv-PPA) is a degenerative condition which causes surface dyslexia/dysgraphia, resulting in reading/writing errors of irregular words with non-transparent grapheme-to-phoneme correspondences (e.g., 'plaid') as opposed to regular words (e.g., 'cat'). According to connectionist models, most authors have attributed this deficit to semantic impairments, but this assumption is at odds with symbolic models, such as the DRC account, stating that the reading/writing of irregulars relies on the mental lexicon. Our study investigated whether sv-PPA affects the lexicon in addition to the semantic system, and whether semantic or lexical deficits cause surface dyslexia/dysgraphia, while challenging the two major models of written language. We explored a cohort of 12 sv-PPA patients and 25 matched healthy controls using a reading and writing task, a semantic task (category decision: living vs. non-living), and a lexical task (lexical decision: word vs. no-neighbor non-word). Correlation analyses were conducted to assess the relationship between reading/writing scores of irregulars and semantic vs. lexical performance. Furthermore, item-by-item analyses explored the consistency of reading/writing errors with item-specific semantic and lexical errors. Results showed that sv-PPA patients are impaired at reading and writing irregular words, and that they have impaired performance in both the semantic and the lexical task. Reading/writing scores with irregulars correlated significantly with performance in the lexical but not the semantic task. Item-by-item analyses revealed that failure in the lexical task on a given irregular word is a good predictor of reading/writing errors with that item (positive predictive value: 77.5%), which was not the case for the semantic task (positive predictive value: 42.5%). Our findings show that sv-PPA is not restricted to semantic damage but that it also comprises damage to the mental lexicon, which appears to be the major factor for surface dyslexia/dysgraphia. Our data support symbolic models whereas they challenge connectionist accounts.
原发性进行性失语症（PPA）的语义变异型是一种退行性疾病，导致表面性失读/失写症，导致具有非透明字形-语音对应关系（例如，“格子呢”）的不规则词的阅读/书写错误，而不是规则词（例如，“猫”）。根据连接主义模型，大多数作者将这种缺陷归因于语义障碍，但这一假设与符号模型（例如 DRC 理论）不一致，该理论指出不规则词的阅读/书写依赖于心理词汇。我们的研究调查了 sv-PPA 是否除了语义系统之外还会影响词汇，以及语义或词汇缺陷是否会导致表面性失读/失写症，同时对书面语言的两个主要模型提出了挑战。我们使用阅读和写作任务、语义任务（类别决策：有生命的与无生命的）和词汇任务（词汇决策：单词与非近邻非单词），对 12 名 sv-PPA 患者和 25 名匹配的健康对照组进行了研究。我们进行了相关分析，以评估不规则词的阅读/书写分数与语义和词汇表现之间的关系。此外，逐项分析探讨了阅读/书写错误与特定项目语义和词汇错误的一致性。结果表明，sv-PPA 患者在阅读和书写不规则词方面存在障碍，并且在语义和词汇任务中表现受损。阅读/书写不规则词的分数与词汇任务但与语义任务显著相关。逐项分析表明，在给定的不规则词上词汇任务失败是该项目阅读/书写错误的良好预测指标（阳性预测值：77.5%），而语义任务则不然（阳性预测值：42.5%）。我们的研究结果表明，sv-PPA 不仅限于语义损伤，还包括心理词汇损伤，这似乎是表面性失读/失写症的主要因素。我们的数据支持符号模型，而对连接主义模型提出了挑战。
