Long-range temporal correlations in the subthalamic nucleus of patients with Parkinson's Disease

Neuronal activity in the subthalamic nucleus (STN) of untreated patients with Parkinson’s disease (PD) is characterized by excessive neuronal synchronization, particularly in the beta frequency range. However, less is known about the temporal dynamics of neuronal oscillations in PD. In this respect long-range temporal correlations (LRTC) are of special interest since they quantify neuronal dynamics on different time scales and were shown to be relevant for optimal information processing in the brain. While the presence of LRTC was demonstrated in cortical data, their existence in deep brain structures remains an open question. We investigated (1) whether LRTC are present in local field potentials (LFP) recorded from bilateral STN at wakeful rest in ten patients with PD after overnight withdrawal of levodopa (OFF), and (2) whether LRTC can be modulated by acute levodopa treatment (ON). Detrended Fluctuation Analysis was utilized in order to quantify the temporal dynamics in amplitude fluctuations of neuronal oscillations. We demonstrated for the first time the presence of LRTC (extending up to 50 sec) in STN. Importantly, the ON state was characterized by significantly stronger LRTC compared to the OFF state, both in beta (13–35 Hz) and high-frequency (> 200 Hz) oscillations. On the other hand, spectral power decreased in the beta band and increased in the high-frequency band during ON medication. The existence of LRTC in subcortical STN provides further evidence for their ubiquitous nature in the brain. The weaker LRTC in the OFF state might indicate limited information processing in the dopamine-depleted basal ganglia. The present results implicate LRTC as a potential biomarker of pathological neuronal processes in PD that may be used for diagnosis and treatment strategies. Supported by DFG KFO 247.