Objectives: 

Imitation can be described as the capacity to learn to do an action from seeing it done. It is possible to design therapies based on imitation for patients with motor impairments and virtual reality (VR) offers a new perspective on such therapies. The dopaminergic system is known to be involved in motor action, but its role in imitation is unknown. The main objective of this study is to understand the role of the dopaminergic system in imitation, by observing and executing (at the same time and in VR) different motor patterns.

Materials: 

10 OFF-dose idiopathic Parkinson's Disease (PD), 9 age-matched and 9 young healthy subjects participated. Subjects were asked to perform finger-tapping movements at their comfort and comfort-slow rates while immersed in a VR system which presented their "avatar" in 1st person perspective. Imitation was evaluated by asking subjects to replicate finger tapping patterns different to their natural one. The finger pattern presented matched their comfort and comfort-slow rates but without resting on the table (finger always moving)

Results: 

When subjects imitated the avatar's finger movements all were able to correctly adapt their finger tapping to the one proposed, showing that in comparison with the control groups, the dopaminergic deficiency of PD did not impair imitation. During imitation the magnitude of EMG increased and the temporal variability of movement decreased.

Conclusions: 

PD patients have unaltered ability to simultaneously imitate motor patterns, suggesting that the dopaminergic system does not rule such imitation. Imitation training may therefore offer a route to motor rehabilitation in aging and PD.