| Despite the fact that bilingualism is common, little is known about the effect of aging or age-related disorders on bilingual speech production. No previous study has contrasted narratives or examined verb inflection in a native (L1) versus a second language (L2) in healthy older adults or patients. We tested 16 young and 16 older adults, and 9 Alzheimer (AD) and 8 Parkinson patients (PD), all French/English bilingual who learned L2 after age 8. Participants described a complex picture (Manuscript 1) and generated the past tense of verbs (Manuscript 2) in L1 and L2. The neurolinguistic models of Paradis (1994) and Ullman (2001) suggest that L2 grammar (when L2 is learned late) and the lexicon are linked to declarative memory, whereas L1 grammar is linked to procedural memory. Given that AD affects mostly declarative memory, and PD procedural memory, AD was expected to chiefly affect the lexicon in L1 and L2, and L2 grammar, and PD to mostly impact L1 grammar. The speech and verb inflection performance of AD patients suggests that AD affects lexical processing more than grammatical processing in L1, and affects L1 more than L2. The speech and verb inflection performance of PD patients suggest greater grammatical than lexical impairment in L1, but both grammatical and lexical difficulties in L2. The L1 findings replicate those in the literature. The L1-L2 findings suggest that AD and PD affect L1 and L2 differently, in a manner that differs from that predicted, and that aging has little effect on picture description and verb inflection. |
