## 2 Materials and Methods  
### Dataset  
In this work, we enrolled 51 patients with idiopathic PD. All of them are Czech native speakers (17 females and 34 males; age: 65.47 \(\pm\) 7.46 years; PD duration: 7.61 \(\pm\) 4.01 years; mean LED (L-dopa equivalent daily dose) [32]: 1033.67 \(\pm\) 567.96 mg/day) at the First Department of Neurology, St. Anne's University Hospital in Brno, Czech Republic. After two years, the patients were re-examined (age: 67.61 \(\pm\) 7.38 years; PD duration: 9.57 \(\pm\) 4.50 years; mean LED: 1115.11 \(\pm\) 484.38 mg/day). All patients signed an informed consent form that has been approved (including the study) in 14 March 2016 by the Research Ethics Committee of Masaryk University (ref. no. : EKV-2016-004, project title: Effects of non-invasive brain stimulation on hypokinetic dysarthria, micrographia, and brain plasticity in patients with Parkinson's disease, investigator: Prof. MD. [PERSON], PhD.). None of the patients had a disease affecting the central nervous system other than PD. All patients were examined on their regular dopaminergic medication approximately 1 h after the L-dopa [32] dose. The following rating scales were used to evaluate the clinical symptoms of PD: UPDRS III and UPDRS IV [3], FOG-Q [4], REM sleep behavior disorder screening questionnaire (RBDSQ) [33], and ACE-R [5]. The full clinical characteristics of the dataset, i.e., mean \(\pm\) sd values for the clinical rating scales in session 1, session 2, and session \(\Delta\) (session 2 - session 1) can be seen in Table 1. Moreover, to identify statistically significant differences, the table reports \(p\)-values of the Wilcoxon signed-rank test between the data acquired in session 1 (baseline examination) and session 2 (two-year follow-up examination) too. The clinical data from the \(\Delta\) session were also used to generate descriptive visualizations (i.e., histograms, regression and residual plots) for the change in selected clinical rating scales, more specifically: LED, UPDRS III, UPDRS IV, FOG-Q, RBDSQ, ACE-R, see Figure 1. With this approach, it is possible to assess the improvement and/or decline in motor and non-motor deficits associated with PD in the horizon of two years as well as a relationship between the change in each of the scales relative to other scales in the selected set. \begin{table}
\begin{tabular}{l c c c c c} \hline \hline
**Scale** & **Mean \(\pm\) sd (s1)** & **Mean \(\pm\) sd (s2)** & **Mean \(\pm\) sd (\(\Delta\))** & \(p\) (Wilcoxon)** \\ \hline LED & 917.61 \(\pm\) 544.78 & 1129.92 \(\pm\) 477.50 & 212.31 \(\pm\) \(-\)67.28 & 0.188 \\ UPDRS III & 22.49 \(\pm\) 13.47 & 27.45 \(\pm\) 12.68 & 4.96 \(\pm\) \(-\)0.79 & 0.000 \\ UPDRS IV & 2.82 \(\pm\) 2.58 & 3.44 \(\pm\) 2.94 & 0.62 \(\pm\) 0.36 & 0.632 \\ FOG-Q & 6.57 \(\pm\) 5.40 & 8.33 \(\pm\) 5.97 & 1.76 \(\pm\) 0.57 & 0.000 \\ RBDSQ & 3.98 \(\pm\) 3.25 & 3.78 \(\pm\) 2.28 & \(-\)0.2 \(\pm\) \(-\)0.98 & 0.522 \\ ACE-R & 87.92 \(\pm\) 7.62 & 85.89 \(\pm\) 9.48 & \(-\)2.03 \(\pm\) 1.86 & 0.000 \\ \hline \hline \end{tabular} s1—first session; s2—second session; \(\Delta\)—delta session (session 2 – session 1); \(p\) (Wilcoxon) — \(p\)-value for Wilcoxon signed-rank test (paired samples); LED—L-dopa equivalent daily dose (mg/day) [32]; UPDRS III—Unified Parkinson’s Disease Rating Scale, part III: evaluation of motor function [3], UPDRS IV—Unified Parkinson’s Disease Rating Scale, part IV: evaluation of complications of therapy [3]; FOG-Q—Freezing of gait questionnaire [4]; RBDSQ—The REM sleep behavior disorder screening questionnaire [33]; ACE-R—Addenbrooke’s Cognitive Examination-Revised [5].  
\end{table} 
Table 1: Clinical characteristics of the patients. Figure 1: Descriptive statistical graphs of clinical characteristics of the PD patient dataset: on the main diagonal, histograms are visualized. Next, the upper triangular part of the graph-grid shows scatter plots with the fitted lines of linear regression models.