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

Overview

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).

Methods: Record STN-cortex LFP coherence pattern and then stimulate STN (at 0, 5, 10, 15, 20, 25, 30 Hz) in newly implanted patients at rest and during simple and complex motor tasks while recording the steady state evoked potential over the cortex using EEG. The resonance frequency will be calculated as previously (Eusebio et al, Brain 2009). Experiments will be carried out both in the OFF medication and ON medication condition.

Conditions