Pattern of local field potential activity in the globus pallidus internum of dystonic patients during walking on a treadmill

The basal ganglia (BG) are involved in gait. This notion is exemplified by observations that gait is disturbed by most diseases that affect the BG. However, it is unclear in what way the BG are activated during gait. One method to investigate the activity of the BG is to record local field potentials (LFPs) from electrodes placed in the BG for therapeutic purposes. Nowadays, the globus pallidus internum (GPi) represents the target for deep brain stimulation (DBS) in dystonia. LFPs recorded from this area have been shown to delineate activity associated with dystonic cramps but also activity that may be relevant for certain types of movement. In this study we recorded LFPs from DBS electrodes implanted into the GPi of eight patients with dystonia during walking on a treadmill machine and compared these data with data acquired during rest (sitting and standing). There was no difference in the power of frequency bands during the sitting and standing conditions. LFP power in the theta (4-8 Hz), alpha (8-12 Hz) and gamma (60-90 Hz) frequency bands was higher during walking than during the resting conditions. Beta (15-25 Hz) frequencies were the only frequencies that were down-regulated during walking. The amplitude of the theta and alpha frequency bands was modulated during the gait cycle. These data shed light on the function of the BG in patients with dystonia and demonstrate that, during gait, their overall activity increases in a specific way without showing increases of narrow frequency bands.