An exemplar of the effect of thalamic stimulation at fT in a patient with Parkinson’s disease. During stimulation at 4 Hz (A) median tremor frequency remained at 3.8 Hz, while (B) tremor phase during stimulation was pulled to the phase quadrant extending from 210 to 330° indicating significant tremor entrainment. Tremor phase when stimulation was switched off did not show any clear phase preference. Outer circle of the polar plot corresponds to tremor phase likelihood of 0.1, whereas the inner circle corresponds to tremor phase likelihood of 0.05. (C) During stimulation at fT, the instantaneous amplitude, derived from the tremor envelope, was not modulated depending on the timing of stimulation pulses with respect to the tremor cycle. Significance was assessed at each phase bin with respect to instantaneous tremor amplitude variability when stimulation was switched off using the Wilcoxon rank sum test and significance levels corrected for multiple comparisons using the false discovery rate procedure. Circles show median change in tremor amplitude and shaded regions indicate the 95th confidence intervals of the median values.
