Fig. 4

Average tremor peak frequencies of the training group, 32 PD (a) and 20 ET (b) subjects, while performing kinetic (cross), postural (star) and resting (square) task. Average peak frequency is the mean value of peak frequencies obtained from power spectral density of ten tremor subsequences. The power spectral density was obtained parametrically by autoregressive (AR) model parameters using Yule–Walker method