Parkinson's disease (PD), which involves the degeneration of dopaminergic neurons in the basal ganglia, has long been associated with motor deficits. Increasing evidence suggests that language can also be impaired, including aspects of syntactic and lexical processing. However, the exact pattern of these impairments remains somewhat unclear, for several reasons. 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 PD, 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. We addressed these gaps by investigating multiple aspects of Farsi syntactic and lexical processing in 40 Farsi native-speaking moderate-to-severe non-demented PD patients, and 40 healthy controls. 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 PD 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. No other correlations were found between syntactic/lexical processing measures and either levodopa equivalent dose or hypokinesia, which reflects degeneration of basal ganglia motor-related circuits. All critical significant main effects, interactions, and correlations yielded large effect sizes. The findings elucidate the nature of syntactic and lexical processing impairments in PD.

中文翻译：

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帕金森病句法与词汇加工的分离

帕金森病 (PD) 涉及基底神经节中多巴胺能神经元的退化，长期以来一直与运动障碍有关。越来越多的证据表明，语言也可能受到损害，包括句法和词汇处理的各个方面。然而，由于多种原因，这些损伤的确切模式仍然有些不清楚。很少有研究检查和比较受试者内部的句法和词汇加工，因此它们的相对缺陷仍有待阐明。研究集中在 PD 的早期阶段，因此对后期阶段的句法和词汇处理了解较少。研究主要探讨了英语和少数其他欧洲语言，尚不清楚调查结果是否具有更广泛的概括性。最后，很少有研究检查句法/词汇障碍与其神经认知底物之间的联系，例如基底神经节变性或多巴胺能过程的测量。我们通过调查 40 名波斯语母语中度至重度非痴呆 PD 患者和 40 名健康对照的波斯语句法和词汇处理的多个方面来解决这些差距。分析表明，在不同的句法结构中，句法理解和句法判断存在相同的损害。词汇加工仅对运动功能相关的对象（例如，命名“锤子”，而不是“山”）受损，这与 PD 在命名动作动词时与对象相比存在缺陷的发现一致，没有动词/名词混淆。在词汇和句法任务之间的直接比较中，与句法理解和句法判断相比，患者更擅长命名像“山”这样的词（但不是像“锤子”这样的词）。句法理解的表现与最后的左旋多巴等效剂量相关。在句法/词汇处理措施与左旋多巴等效剂量或运动机能减退之间没有发现其他相关性，这反映了基底神经节运动相关回路的退化。所有关键的显着主效应、交互作用和相关性都会产生较大的效应量。研究结果阐明了 PD 中句法和词汇处理障碍的性质。在句法/词汇处理措施与左旋多巴等效剂量或运动机能减退之间没有发现其他相关性，这反映了基底神经节运动相关回路的退化。所有关键的显着主效应、交互作用和相关性都会产生较大的效应量。研究结果阐明了 PD 中句法和词汇处理障碍的性质。在句法/词汇处理措施与左旋多巴等效剂量或运动机能减退之间没有发现其他相关性，这反映了基底神经节运动相关回路的退化。所有关键的显着主效应、交互作用和相关性都会产生较大的效应量。研究结果阐明了 PD 中句法和词汇处理障碍的性质。