To investigate cortical oscillations in Parkinson’s disease (PD) at the time of foot movements and their response to dopaminergic therapy.

Elevated high-beta EEG power (high-β, 21-35 Hz) in the sensorimotor cortex has been reported in PD. Elevated high-β is hypothesized to be disruptive to movement. Dopaminergic medication reduced cortical high-β in a rodent model of PD. However, it is unclear whether PD medication desynchronizes high-β generally or specifically at the time of movement.

Whole-head EEG was recorded from 15 PD patients [2 women; median age 65 years, range 57-79; median PD duration 8 years, range 1-20; median levodopa equivalent daily dose 650 mg, range 300-1880]. Patients were assessed while ON dopaminergic medication (PD-ON) and OFF medication after 12-hour withdrawal (PD-OFF). We also tested 15 age-matched healthy controls (HC). Rest EEG was measured while participants passively viewed forward movement down a virtual hallway but did not step. For active step trials, participants had to step alternately with foot pedals to move through the virtual hallway. High-β power was assessed at rest and active trials. We then assessed high-β at “high-intensity” toe-down periods of the right foot and at “low-intensity” periods between toe-down periods. The difference in high-β between “high-intensity” and “low-intensity” phases was determined at premotor/frontal, motor, and parietal clusters and compared between PD-ON versus PD-OFF and between PD-ON versus HC.  

PD-ON and PD-OFF had similar levels of cortical high-β power. HC dramatically reduced cortical high-β power from rest to stepping, but this effect was not seen in PD-OFF nor PD-ON. In all cortical clusters, high-β desynchronized from high-to-low intense periods in PD-ON compared to PD-OFF. High-β desynchronization from high-to-low intensity did not differ between PD-ON and HC.  

Dopaminergic medications desynchronized cortical high-beta power specific to the time of movement. High-beta desynchronization may play a role in motor improvements.