Fig. 2. Amplitude-vs.-velocity relationship (“main sequence”) for square-wave jerks pooled for all progressive supranuclear palsy patients (dots and solid line), all Parkinson's disease patients (crosses and dashed line), and all control subjects (dotted line). No differences are evident in either target-on or target-off condition. To improve clarity, only the fitted curve (and not the single data points) is shown for the control subjects.