Few studies have examined and compared syntactic and lexical processing within subjects, so their relative deficits remain to be elucidated. Studies have focused on earlier stages of Parkinson’s disease, so syntactic and lexical processing in later stages are less well understood. Research has largely probed English and a handful of other European languages, and it is unclear whether findings generalize more broadly. Finally, few studies have examined links between syntactic/lexical impairments and their neurocognitive substrates, such as measures of basal ganglia degeneration or dopaminergic processes.
The researchers addressed these gaps by investigating multiple aspects of Farsi syntactic and lexical processing in 40 Farsi native-speaking moderate-to-severe non-demented Parkinson’s patients, and 40 healthy controls. Their analyses revealed equivalent impairments of syntactic comprehension and syntactic judgment, across different syntactic structures.
Lexical processing was impaired only for motor function-related objects (e.g., naming ‘hammer’, but not ‘mountain’), in line with findings of Parkinson’s deficits at naming action verbs as compared to objects, without the verb/noun confound. In direct comparisons between lexical and syntactic tasks, patients were better at naming words like ‘mountain’ (but not words like ‘hammer’) than at syntactic comprehension and syntactic judgment. Performance at syntactic comprehension correlated with the last levodopa equivalent dose.Friday Letter Submission