Subject characteristics and performance on cognitive tasks.

<p>Values reported are sums, mean (SD), or median (range). Abbreviations: BTA = Brief Test of Attention; HC = healthy control; MMSE = Mini-Mental State Examination; MSAp = parkinsonian variant of multiple system atrophy; MVC = maximum voluntary contraction; <i>ns</i> = not significant; PD = Parkinson’s disease; PSP = progressive supranuclear palsy; UPDRS = Unified Parkinson’s Disease Rating Scale.</p

Receiver operating characteristic (ROC) curves for (A) individual and (B) combined variables.

<p>Abbreviations: AUC = Area under the curve; BTA = Brief Test of Attention; MSAp = parkinsonian variant of multiple system atrophy; MMSE = Mini-mental state exam; PD = Parkinson's disease; PSP = progressive supranuclear palsy.</p

Participants completed two precision grip force tasks.

<p>A: the precision grip apparatus held with a modified grip. B: the visual display contained two horizontal bars presented against a high contrast black background. The target bar (red/green) was stationary during each force pulse, whereas the white force bar moved to provide online visual feedback. In both force tasks, participants produced 10, 2 s force pulses separated by 1 s of rest. C: in the SAME task, target amplitude was 15% of the participant’s MVC on all force pules. D: in the DIFF task, the target amplitude varied unpredictably from pulse to another. E: four time-points were determined for each force pulse as shown here. Arrow 1 marks the onset of force. Arrow 2 marks the onset of the steady force interval and arrow 3 marks the end of the steady force interval. Arrow 4 marks force offset. The rate of force increase is the slope of the black line between arrows 1 and 2. The duration of the force pulse is the time between arrows 2 and 3. The rate of force decrease is the slope of the black line between arrows 3 and 4. Mean force is calculated as the average force output between arrows 2 and 3. Variability of force output is the standard deviation of mean force.</p