PMC

(A) Dopamine response (on the y-axis, tremor power “off” minus “on,” ± SEM) for resting and re-emergent tremor, with a larger dopamine response for rest tremor than for re-emergent tremor (same patient group). (B, C) Correlation of (log-transformed) tremor power (B) and dopamine response (log-transformed tremor power “off” minus “on” corrected for absolute “off” state tremor power, C) between resting tremor (x-axis) and re-emergent tremor (y-axis). The dashed lines indicate a reference line when x = y.

The difference between re-emergent and pure postural tremor for Δ frequency (A; postural minus rest tremor frequency), dopamine response (B; mean tremor power in “off” minus “on”), and the effect of wrist extension on tremor amplitude (C; log-transformed tremor power at individual tremor frequency ± 1.5 Hz to accommodate slight changes in tremor frequency).

Kinetic tremor score by category of postural tremor (0, 0.5, 1, 1.5, 2, 2.5, 3). The top panel shows the mean kinetic tremor scores in cases with mean postural tremor score=0. The bottom panel shows the mean kinetic tremor scores in cases with a mean postural tremor score=3. The yellow background indicates cases in whom the mean kinetic tremor score was greater or equal to the mean postural tremor score. For example, among 131 cases with a mean postural tremor score=1, only 2 (1.5%) had a mean kinetic tremor score <1.

Relationship between tremor amplitude modulation during stimulation at near postural tremor frequency (f_T) and the degree of tremor entrainment. Although tremor suppression was inversely proportional to tremor entrainment, tremor amplification did not show any dependency, possibly because tremor amplitude was already at ceiling values and could not be amplified further. Linear regression fits (thick grey lines) and their 95% confidence limits (thin grey lines) are shown in each panel. (A) Lower panel (in blue): tremor suppression showed a trend towards dependency on tremor entrainment at the tremor axis that showed maximal change in tremor amplitude (F-statistic P = 0.0803, R² = 0.3336). Upper panel (in red): in contrast, tremor amplification did not show any dependency on tremor entrainment at the same axis (F-statistic P = 0.9155, R² = 0.0015). (B) This difference between suppression and amplification was confirmed when changes across all three axes of the tri-axial accelerometer were considered. Lower panel: tremor suppression was inversely proportional to tremor entrainment (F-statistic P = 1 × 10⁻⁴, significant following FDR correction, R² = 0.4171), confirming the relationship between amplitude suppression and entrainment. Upper panel: tremor amplification did not show dependency on tremor entrainment (F-statistic P = 0.4089, R² = 0.0245).