In patients with PD, we found that dynPAC was abnormal during slow tapping. Although patients attained similar PAC strengths levels before initiating the tapping movements, the subsequent decrease was smaller than that in controls. As was the following rebound. By contrast, during the press and release, dynPAC modulation was similar in patients and controls. These findings appear to be the first to report that abnormal PAC during movement is associated with concurrent abnormal motor performance in PD. If the above proposal that dynPAC is a marker for a preparatory movement state is in fact true, patients with PD may suffer from a defective evolution of a neuronal population dynamic, spanning the preparatory state and overt movement generation. Although PAC would reflect an essential physiological mechanism during the preparation of movements, its persistence into the unfolding movement would interfere with proper execution. Although abnormal dynPAC modulation was associated with slowed muscle recruitment during onset of slow tapping, the magnitude of PAC change did not correlate with the magnitude of the EMG slope. This suggests a complex and non-linear relationship between dynPAC
