gms | German Medical Science

Objective: Local field potential (LFP) oscillations in the 13–30 Hz frequency band are related to the pathophysiology of the basal ganglia of Parkinson's disease with beta activity in LFP being reduced in PD patients during movement or following medication. The current study was performed based on the hypothesis that these pathophysiological oscillations modulate during gait in Parkinson's disease while subjects experience freezing and non-freezing phenomena.

Methods: We recorded LFPs from (still externalized) deep brain stimulation electrodes implanted into the subthalamic nucleus (STN) of 6 Parkinson patients during rest (sitting and standing condition) and gait (walking condition) on a treadmill machine with preferred velocity. Parkinson patients were grouped into subjects without freezing i.e. non-freezer (n=3) and subjects with freezing i.e. freezer (n=3). LFP signals were sampled at 2.5 kHz and filtered (band passed) at 1–90 Hz.

Results: LFP power in the 13–20 Hz (low beta) frequency band was diminished during gait in non-freezing Parkinson subjects, while freezing subjects had a prominent 13–20 Hz peak during gait compared with the resting condition.

Conclusions: Prominent low beta frequency activity may be causal for gait impairment or freezing of gait. Non-freezers had low beta frequency peaks during rest but were able to “reduce” this type of activity during walking. In freezers, this activity became prominent during walking. Possibly different modes of basal ganglia functions are accompanied by separate prominent rhythms and PD patients are not capable of switching these modes in a way which would be necessary for the smooth performance of the desired movement.