Lexico-semantic processing in individuals with Alzheimer’s disease : evidence from picture naming task in Iranian Azerbaijani Turkish-Persian bilinguals

Abstract

Adopting a linguistic approach to the pathology of the mind on bilinguals afflicted with aphasia caused by Alzheimer's disease (AD) has given rise to a wide array of interdisciplinary research in recent years. However, bilinguals’ language impairments in AD have not been appropriately experimentally investigated while language deterioration has always been a frequent symptom of AD. A task-based research in this study has been conducted to investigate the effect of Anomic Aphasia caused by AD on the lexico-semantic skills of Iranian Azerbaijani Turkish-Persian bilingual women. To this end, the experimental group (AD) with 20 participants with Mini-Mental State Examination (MMSE) test scores in the range of 19 and 23 were matched in terms of age, age of familiarity with Persian language, and formal education. There was also a control group consisting of 20 participants with Mild Cognitive Impairment (MCI) and having MMSE test scores in the range of 23 and 30. The verbal productions of both groups were evaluated by the Bilingual Aphasia Picture Naming Task (BAT) in the Azerbaijani Turkish and Persian languages separately. Comparing the average reaction times (RTs) to the stimulus pictures in two languages showed that AD affected the nondominant language (Persian) more severely than the dominant language (Azerbaijani Turkish). The results of this research are consistent with the three-store hypothesis in the framework of the Neurolinguistic Notion of Bilingualism maintaining that bilinguals have two language subsystems, each of which has an independent and separate grammar and vocabulary, and a non-linguistic cognitive system.