Dynamic Variability of Isometric Action Tremor in Precision Pinching

Figure 5

Scatter plot of the thumb-index finger power difference variable against total tremor power using values from all trial segments of both the PD and OA groups, although data from the OA group are too clustered for resolution of individual points. Limiting boundaries where all tremor power comes from a single digit are designated with dashed lines. As total tremor power increases beyond background level, the points remain close to the boundary lines, indicating a substantial asymmetry between the digits, with thumb dominance occurring in most instances.