Pallidal and Cortical Oscillations in Freely Moving Patients With Dystonia

Objectives: To evaluate the correlation between the pallidal local eld potentials (LFPs) activity and the cortical oscillations (at rest and during several motor tasks) in two freely moving patients with generalized dystonia and pallidal deep brain stimu- lation (DBS). Materials and Methods: Two women with isolated generalized dystonia were selected for bilateral globus pallidus internus (GPi) DBS. After the electrodes’ implantation, cortical activity was recorded by a portable electroencephalography (EEG) system simultaneously with GPi LFPs activity, during several motor tasks, gait, and rest condition. Recordings were not performed dur- ing stimulation. EEG and LFPs signals relative to each specic movement were coupled together and grouped in neck/upper limbs movements and gait. Power spectral density (PSD), EEG-LFP coherence (through envelope of imaginary coherence oper- ator), and 1/f exponent of LFP-PSD background were calculated. Results: In both patients, the pallidal LFPs PSD at rest was characterized by prominent 4–12 Hz activity. Voluntary movements increased activity in the theta (θ) band (4 –7 Hz) compared to rest, in both LFPs and EEG signals. Gait induced a drastic raise of θ activity in both patients’ pallidal activity, less marked for the EEG signal. A coherence peak within the 8–13 Hz range was found between pallidal LFPs and EEG recorded at rest. Conclusions: Neck/upper limbs voluntary movements and gait suppressed the GPi-LFPs—cortical-EEG coherence and differ- ently impacted both EEG and LFPs low frequency activity. These ndings suggest a selective modulation of the cortico-basal ganglia network activity in dystonia.