Do Acoustic Characteristics of Dysarthria in People With Parkinson's Disease Differ Across Languages?

PURPOSE: Cross-language studies suggest more similarities than differences in how dysarthria affects the speech of people with Parkinson's disease (PwPD) who speak different languages. In this study, we aimed to identify the relative contribution of acoustic variables to distinguish PwPD from controls who spoke varieties of two Romance languages, French and Portuguese. METHOD: This bi-national, cross-sectional, and case-controlled study included 129 PwPD and 124 healthy controls who spoke French or Portuguese. All participants underwent the same clinical examinations, voice/speech recordings, and self-assessment questionnaires. PwPD were evaluated off and on optimal medication. Inferential analyses included Disease (controls vs. PwPD) and Language (French vs. Portuguese) as factors, and random decision forest algorithms identified relevant acoustic variables able to distinguish participants: (a) by language (French vs. Portuguese) and (b) by clinical status (PwPD on and off medication vs. controls). RESULTS: French-speaking and Portuguese-speaking individuals were distinguished from each other with over 90% accuracy by five acoustic variables (the mean fundamental frequency and the shimmer of the sustained vowel /a/ production, the oral diadochokinesis performance index, the relative sound level pressure and the relative sound pressure level standard deviation of the text reading). A distinct set of parameters discriminated between controls and PwPD: for men, maximum phonation time and the oral diadochokinesis speech proportion were the most significant variables; for women, variables calculated from the oral diadochokinesis were the most discriminative. CONCLUSIONS: Acoustic variables related to phonation and voice quality distinguished between speakers of the two languages. Variables related to pneumophonic coordination and articulation rate were the more effective in distinguishing PwPD from controls. Thus, our research findings support that respiration and diadochokinesis tasks appear to be the most appropriate to pinpoint signs of dysarthria, which are largely homogeneous and language-universal. In contrast, identifying language-specific variables with the speech tasks and acoustic variables studied was less conclusive.

Subthalamic stimulation breaks the balance between distal and axial signs in Parkinson's disease.

In Parkinson's disease (PD), the effects of both Ldopa and subthalamic deep brain stimulation (STN-DBS) are known to change cost-valuation. However, this was mostly studied through reward-effort task involving distal movements, while axial effort, less responsive to treatments, have been barely studied. Thus, our objective was to compare the influence of both Ldopa and STN-DBS on cost-valuation between two efforts modalities: vowel production (as an example of axial movement) and hand squeezing (as an example of distal movement). Twelve PD patients were recruited to participate in this study. The task consisted in deciding whether to accept or reject trials based on a reward-effort trade-off. Participants performed two blocks with hand squeezing, and two with vowel production, in the four treatment conditions (Ldopa On/Off; STN-DBS On/Off). We found that STN-DBS changed the ratio difference between hand and phonation efforts. Vowel production effort was estimated easier to perform with STN-DBS alone, and harder when associated with Ldopa. The difference between hand and phonation efforts was correlated with quality of life in Off/Off and On Ldopa alone conditions, and with impulsive assessment On STN-DBS alone. We highlighted that STN-DBS could introduce an imbalance between the actual motor impairments and their subjective costs. With this finding, we also suggest paying particular attention to the different treatment effects that should be expected for axial and distal movement dysfunctions.

Effects of subthalamic nucleus stimulation and levodopa on decision-making in Parkinson's disease.

BACKGROUND: Parkinson's disease (PD) is frequently associated with behavioral disorders, particularly within the spectrum of motivated behaviors such as apathy or impulsivity. Both pharmacological and neurosurgical treatments have an impact on these impairments. However, there still is controversy as to whether subthalamic nucleus deep brain stimulation (STN-DBS) can cause or reduce impulsive behaviors. OBJECTIVES: We aimed to identify the influence of functional surgery on decision-making processes in PD. METHODS: We studied 13 PD patients and 13 healthy controls. The experimental task involved squeezing a dynamometer with variable force to obtain rewards of various values under four conditions: without treatment, with l-dopa or subthalamic stimulation alone, and with both l-dopa and subthalamic stimulation. Statistical analyses consisted of generalized linear mixed models including treatment condition, reward value, level of effort, and their interactions. We analyzed acceptance rate (the percentage of accepted trials), decision time, and force applied. RESULTS: Comparatively to controls, patients without treatment exhibited lower acceptance rate and force applied. Patients under l-dopa alone did not exhibit increased acceptance rate. With subthalamic stimulation, either with or without added l-dopa, all measures were improved so that patients' behaviors were undistinguishable from healthy controls'. CONCLUSIONS: Our study shows that l-dopa administration does not fully restore cost-benefit decision-making processes, whereas STN-DBS fully normalizes patients' behaviors. These findings suggest that dopamine is partly involved in cost-benefit valuation, and that STN-DBS can have a beneficial effect on motivated behaviors in PD and may improve certain forms of impulsive behaviors. © 2019 International Parkinson and Movement Disorder Society.