Pathophysiology of Neuronal Oscillations Within Subthalamo-cortical Loops in Parkinson's Disease

Neuronal activity in circuits between the basal ganglia (BG) and motor cortical areas is abnormally synchronised and rhythmic. The oscillatory activity prevails at 8-30 Hz in untreated Parkinson's Disease (PD) and its amplitude at both subthalamic and cortical levels inversely correlates with motor impairment. Moreover, these different levels in BG-cortical loops are coherent in this frequency band. The 8-30 Hz activity is suppressed by treatment following treatment with dopaminergic drugs and is partially suppressed prior to and during voluntary movements. An unanswered question is how do BG-cortical loops become so prominently engaged in this oscillatory activity? One possible explanation is that the resonance frequencies of the loops fall in the 8-30 Hz band in the untreated state, so that oscillations in this band are transmitted particularly well. This hypothesis was confirmed in a previous series of experiments.The aim is to determine whether the resonance frequency within BG-cortical loops is correlated to the BG-cortical coherence frequency (with 20 subjets during 24 months).