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Figure 7. Distribution of peak velocity in all trials (valid and void) for each condition. Labels for the conditions are as in Figure 2. A, Histogram representation of peak velocity distributions. Each panel shows, for a single condition, the number of movements, averaged across subjects in each group, with peak velocity in the range defined by each bin (bin width, 5 cm/s). Thin black lines indicate data from patients, and thick gray lines indicate data from control subjects. Dashed vertical lines mark the range of required speeds for each condition: movements within these lines are valid trials; those outside are void trials. Note that the scale of the horizontal axes is the same across all panels; differences in range are attributable only to horizontal shifts. The scale of the vertical axes is the same for all panels. B, Nonparametric probability density estimation of peak velocity distributions, based on same data as in A. Each trace is the sum of normalized Gaussian functions (SD, 2.5 cm/s), with each movement contributing a Gaussian function (kernel) centered on its peak velocity (Silverman, 1986). This sum is an estimate of the probability density function underlying movement speed distributions. The vertical axis indicates the number of movements, averaged across subjects in each group, with peak velocity within 1 cm of the corresponding x-axis value. Note that the functions are not normalized, to allow comparison of distributions between subject groups and across conditions. Shading indicates the difference between patients' and control subjects' distributions for void trials. Trace thickness, trace shading, and horizontal axes are as in A. CTL, Control.
