Sex, dopamine, and hypokinesia: A study of inflectional morphology in Parkinson’s disease.

Abstract

Objective: Parkinson’s disease (PD), which involves the degeneration of dopaminergic basal ganglia neurons, appears to affect language. We investigated which aspects of language are impaired in PD and what moderates these impairments. Our predictions were based on the declarative/procedural model of language, which links grammar, including in regular inflection, to procedural memory and left-lateralized basal ganglia dopaminergic circuits but links lexical memory, including irregulars, to declarative memory. Because females tend to show declarative memory advantages as compared to males, the model predicts that females rely more on this system for regulars, which can be stored as chunks. Method: We probed regular/irregular Farsi past-tense production in 40 Farsi-speaking patients with moderate-to-severe nondemented PD (half female) and 40 normal controls (half female). Results: Consistent with our predictions, we found that male, but not female, PD patients showed greater deficits at regular than irregular past-tense production. The females’ impairment was mildest for regulars, likely from compensatory storage, as revealed by regular past-tense frequency effects only in females. Right-side hypokinesia (linked to left basal ganglia degeneration) correlated negatively with accuracy of regulars but not irregulars. Similarly, the levodopa equivalent dose of patients’ last medication correlated only with regulars. Conclusions: The results suggest that language is impaired in PD, but the impairments are moderated by multiple factors, including the type of linguistic knowledge, the degree of left basal ganglia degeneration, dopamine, and sex. The findings underscore the impact of sex on the neurocognition of language and the roles of left basal ganglia dopaminergic circuits in aspects of rule-governed grammar.

Theta Oscillations within Right Dorsolateral Prefrontal Cortex Contribute Differently to Speech vs. Limb Inhibition

“…To further explore stimulation effects on the accuracy rate for speech vs. limb No-Go, post-hoc pairwise comparisons were performed. Moreover, since subjects showed a high level of performance on the No-Go trials (see Table 2), we normalized our data using log-odds transformation: natural log (number correct + 0.5/number incorrect + 0.5), where .5 added to avoid 0 in the denominator (Jaeger, 2008;Johari, Walenski, Reifegerste, Ashrafi, & Ullman, 2019). We submitted the logodds of No-Go accuracy into a repeated-measures ANOVA, using modality and stimulation as within-subject factors to verify the results of our logistic mixed effect models.…”

Sex differences in effects of tDCS and language treatments on brain functional connectivity in primary progressive aphasia

“…However, recent studies show that sex may be a biological factor that differentiates progression of symptoms in PPA ( Breining et al, under review ). Importantly, studies in other neurodegenerative disorders, and Parkinson’s Disease (PD) in particular, have shown sex differences in important aspects of language processing, such as morphology ( Johari et al, 2019 , Reifegerste et al, 2020 , Ullman et al, 2008 ).…”