Abstract Objective Deep brain stimulation in the globus pallidus internus (GPi) is used to alleviate the motor symptoms of both Parkinson’s disease (PD) and dystonia. We tested the hypothesis that PD and dystonia are characterized by different temporal patterns of synchronized oscillations in the GPi, and that the dopaminergic loss in PD makes the basal ganglia more susceptible to oscillatory activity. Methods Neuronal firing and local field potentials (LFPs) were simultaneously recorded from the GPi in four PD patients and seven dystonia patients using two independently driven microelectrodes. Results In the PD patients, beta (11–30 Hz) oscillations were observed in the LFPs and the firing activity of ∼30% of the neurons was significantly coherent with the LFP. However, in the dystonia group, the peak frequency of LFP oscillations was lower (8–20 Hz) and there was a significantly smaller proportion of neurons (∼10%) firing in coherence with the LFP ( P < 0.001). Conclusions These findings suggest that synchronization of neuronal firing with LFP oscillations is a more prominent feature in PD than in dystonia. Significance This study adds to the growing evidence that dopaminergic loss in PD may increase the sensitivity of the basal ganglia network to rhythmic oscillatory inputs.