Sentence production in Parkinson's disease.

While growing evidence reports changes in language use in non-demented individuals with Parkinson's disease (PD), the presence and nature of the deficits remain largely unclear. Researchers have proposed that dysfunctioning fronto-basal ganglia circuit results in impaired grammatical processes, predicting qualitatively similar language impairments between individuals with PD and agrammatic Broca's aphasia, whereas others suggest that PD is not associated with language-specific grammatical impairment. In addition, there is a paucity of research examining syntactic production in PD at the sentence-level. This study examined sentence production of individuals with PD, healthy older adults, and individuals with agrammatic Broca's aphasia. In Experiment 1, using a Cinderella story-telling task, proportion of grammatical sentences, number of embedded clauses and production of verb arguments in sentences were examined. In Experiment 2, a structured sentence elicitation task was used in which syntactic complexity of sentences (canonical vs. non-canonical word order) was systematically manipulated while minimizing demands for non-syntactic processing. Only the participants with agrammatic Broca's aphasia showed significantly impaired syntactic production in both experiments. Participants with PD did not show impaired syntactic production in either task, despite impairments in lexical retrieval, repetition of words and sentences, and speech production. These findings suggest that impaired syntactic processing may not be a core deficit underlying the changes in language use in non-demented PD. Changes in language use in PD are qualitatively different from language deficits in aphasia.

Language planning and pauses in story retell: Evidence from aging and Parkinson's disease.

We examined if and how pauses during connected speech reflect cognitive processes underlying language formulation in typical aging and Parkinson's disease (PD), beyond respiratory and motor-speech mechanisms. The frequency of silent pauses was measured (a) in relation to different linguistic (independent clausal, subordinate clausal, phrasal, and atypical) boundaries and (b) proficiency measures of language production in young adults, older adults, and individuals with PD. At the group level, aging, but not PD, resulted in increased pausing at atypical linguistic locations. However, in both aging and PD, individuals' reduced production of syntactically complex sentences was associated with more frequent pausing at various typical prosodic (clausal or phrasal) boundaries. Frequency of pauses was not associated with individual performance in grammaticality of sentences and lexical-semantic production. Overall, the present study demonstrated that production of pauses during connected speech reflects cognitive processes underlying language production beyond respiratory-physiological processes of communication. Assessing production of pauses in connected speech may augment, but does not replace, assessment of language production in clinical practice.