Figure 4.

Schematic presentation of a spectrum of handwriting abnormalities in patients with Parkinson's disease (PD). Note that certain parameters of handwriting, such as velocity and acceleration, are dependent on others, such as amplitude and size, respectively. Therefore, although the figure depicts the spectrum of handwriting abnormalities in PD, they may not be independent, as indicated in the figure. NIV indicates number of inversions of velocity; NIA, inversions of acceleration; RDP, ratio of deceleration phase.