Oscillation and synchronization of neuronal activity has been forwarded as a means of binding distributed sets of neurons into functionally coherent ensembles to serve a variety of cognitive and motor functions.Studies on patients with Parkinsons disease (PD) and in animal models have observed enhanced synchronization of oscillations in several frequency bands within and between the cortical-basal ganglia (BG) structures, and that such activity can be reduced by dopaminergic treatments.It now appears that oscillation and synchronization may play a significant role in the pathogenesis of PD.While attention to features during the waking state has been successful, few researches have reported altered oscillation and synchrony during rapid eye movement (REM) sleep in PD.Here, we simultaneously recorded local field potential and electrocorticogram in globus pallidus (GP)and primary (M1) and secondary (M2) motor cortex on freely moving 6-hydroxydopamine (6-OHDA) lesioned and control rats.Results showed that during REM sleep: (1) Relative power at theta band in M1 cortex of 6-OHDA lesioned rats was significantly smaller than that for control rats.(2) Theta coherence between M1 and any other recording sites (i.e.GP or M2)were significantly decreased by dopamine depletion.To our knowledge, it was the first time to show that 6-OHDA caused decreased synchrony during REM sleep in the cortical-BG loop,which may be underlying the mechanism of REM sleep dyscontrol in PD.