The neural correlates of movement imagery performance in Parkinson's disease: Evidence of impairment and compensation.

Parkinson's Disease (PD) leads to significant deficits in the physical execution of movements. These deficits may stem in part from impaired processing of action representations, which are integral to the planning, monitoring, and execution of voluntary movement. Action representations can be examined using movement imagery. Here we examine whether PD affects movement imagery at the level of behaviour and neural activity. In particular, 20 people with PD and 20 controls completed a movement imagery task while electroencephalographic activity was recorded. Our data analysis focused on activity in the mu rhythm (8-14 Hz) as suppression in this rhythm is associated with sensorimotor network activation and the theta rhythm (3.5-7 Hz), which is proposed to support sensorimotor integration. The PD group was significantly less accurate when imagining successive movements as compared to controls. Successful trials were accompanied by more mu suppression as compared to unsuccessful trials in the control group, but no such effect was observed in the PD group. This result suggests that PD participants relied less on the sensorimotor network to imagine the target movements. Additionally, the PD group exhibited significantly more theta activity over the temporo-occipital region. This increase in theta oscillations may represent increased activity in the extrastriate body area. Taken together, the findings of the present study indicate that impaired processing of action representations may contribute to the motor deficits observed in PD.