Aphasia in Persian: Implications for cognitive models of lexical processing

Current models of oral reading assume that different routes (sublexical, lexical, and semantic) mediate oral reading performance and reliance on different routes during oral reading depends on the characteristics of print to sound mappings. Studies of single cases of acquired dyslexia in aphasia have contributed to the development of such models by revealing patterns of double dissociation in object naming and oral reading skill that follow brain damage in Indo-European and Sino-Tibetan languages. Print to sound mapping in Persian varies in transparency because orthography to phonology translation depends uniquely on the presence or absence of vowel letters in print. Here a hypothesis is tested that oral reading in Persian requires a semantic reading pathway that is independent of a direct non-semantic reading pathway, by investigating whether Persian speakers with aphasia show selective impairments to object naming and reading aloud. A sample of 21 Persian speakers with aphasia ranging in age from 18 to 77 (mean = 53, SD = 16.9) was asked to name a same set of 200 objects and to read aloud the printed names of these objects in different sessions. As an additional measure of sublexical reading, patients were asked to read aloud 30 non-word stimuli. Results showed that oral reading is significantly more preserved than object naming in Persian speakers with aphasia. However, more preserved object naming than oral reading was also observed in some cases. There was a moderate positive correlation between picture naming and oral reading success (p < .05). Mixed-effects logistic regression revealed that word frequency, age of acquisition and imageability predict success across both tasks and there is an interaction between these variables and orthographic transparency in oral reading. Furthermore, opaque words were read less accurately than transparent words. The results reveal different patterns of acquired dyslexia in some cases that closely resemble phonological, deep, and surface dyslexia in other scripts - reported here in Persian for the first time.