Dyslexia phenotypes in Chinese‐speaking individuals with Primary Progressive Aphasia

Abstract

AbstractBackgroundThere are more than 7,000 living languages worldwide with wide heterogeneities in their linguistic features. Varying dementia symptomatology has been noted across speakers of different languages. Chinese languages adopt logographic scripts that contrast greatly from Indo‐European languages with alphabetic writing systems. For instance, Chinese characters have weak grapheme‐phoneme correspondence, with only 19‐ 39% pronounced per their phonetic components. Chinese characters also have 20 different spatial configurations with varying visuospatial complexity and abundant heteronyms. Past literature has focused on the reading presentations of primary progressive aphasia (PPA) patients that adopt Indo‐European languages. This study outlined the reading presentations of Chinese‐speaking PPA patients.MethodThe CLAP (Chinese Language Assessment for PPA) battery is designed to characterize the neurolinguistics features of Chinese‐speaking PPA individuals. In CLAP character reading test, participants are tasked to read aloud 50 Chinese characters that vary in lexicality (pictographic, regular compound, and irregular compound characters), character frequency and concreteness. Voxel‐based morphometry(VBM) was performed to examine the neural basis of reading performance. Participants are also tasked with reading pairs of compound words with heteronyms (e.g., “bow tie” vs “bow down).ResultsA total of 15 Mandarin‐speaking controls and 38 PPA individuals [6 nonfluent variant (nfv) PPA, 9 semantic variant (sv) PPA and 23 logopenic variant (lv) PPA] completed CLAP reading task. In character reading test, svPPA scored significantly lower than controls and nfvPPA (pictographic: p = 0.026; regular compound: p = 0.007; irregular compound characters: p<0.001). Regardless of lexicality, the reading score significantly correlated with volumetric changes over left temporal pole. While over‐regularization errors/surface dyslexia was the most common reading error across control and PPA groups, it was not specific to svPPA (p = 0.109). Conversely, on heteronym word reading test, svPPA and lvPPA scored significantly lower in accuracy, with over‐regularization errors more frequently noted in svPPA group.ConclusionContrary to English svPPA patients that struggled specifically with irregular word reading and showed frequent surface dyslexia, Chinese PPA patients showed no variant‐specific differences across lexicality, and svPPA‐specific over‐regularization phenomenon were found at the lexical (i.e., heteronym‐reading) and not sub‐lexical reading. Diagnostic criteria for PPA syndrome vary with languages and should ideally be tailored linguistically.