Proprioceptive Training And Motor Transfer In Patients With Parkinson’S Disease

Abstract

Parkinson’s disease (PD) is a neurodegenerative disorder that affects the motor system, but is also associated with sensory impairments, such as anosmia or proprioceptive dysfunction. Recent research on healthy individuals shows that a sensorimotor training which challenges the proprioceptive system improves both proprioceptive and motor function. However, it is unknown whether proprioceptive function can be enhanced in PD. It is further unclear, if an improved proprioceptive-motor function after learning leads to general improvements in motor performance. That is, the extent of transfer to other motor tasks is unknown. To fill this knowledge gap, this study employed a robot-aided visuo-proprioceptive motor training to people with PD with the following objectives: First, to identify whether proprioceptive function in Parkinson’s disease (PD) can be enhanced by a visuo-proprioceptive training that emphasizes precise, small amplitude continuous wrist movements. Second, to determine if proprioceptive improvements after training are associated with improvements in an untrained discrete wrist movement task, i.e. demonstrating a sensorimotor transfer within the same joint degree of freedom. Third, to identify if the training transferred to improvements in a functional writing task that relied on multi-joint wrist-hand motion, i.e. showing a sensorimotor transfer for additional joint degrees of freedom. METHOD: 13 participants presenting with mild to moderate PD were tested in their ON medication state. Training involved tilting a virtual table projected on a screen with the aim to position a virtual ball on a target by making continuous and precise small amplitude wrist flexion/extension movements. Wrist position sense acuity, spatial errors for the untrained, goal-directed wrist pointing movement (local transfer) and the more functional hand writing task were assessed before and after training. RESULTS: First, proprioceptive function was improved after training. As a group, PD participants showed a statistically significant reduction in position sense acuity thresholds (mean: pre/post = 1.6° / 1.1°). Second, significant evidence for a localized sensorimotor transfer was found. In the untrained discrete wrist pointing movement, 10 out of 13 participants (77%) recorded improvements in spatial movement precision error (mean: pre/post = 2.4° / 1.8°). Third, spatial error measured in handwriting based tracing and tracking tasks did not show statistically significant training related improvements. CONCLUSION: Wrist proprioceptive function in PD patients can be enhanced with a brief specialized sensorimotor training that emphasizes proprioceptive acuity. Sensorimotor training involving continuous small-amplitude wrist movements improved movement accuracy in an untrained discrete non-visuomotor task. This transfer of spatial motor precision was evident for the same joint degree of freedom, but not in a multiple-joint-degrees-of-freedom handwriting task. These initial findings provide evidence that visuo-proprioceptive training can enhance proprioceptive function in PD. Moreover, they reveal that somatosensory-based training may generalize to other motor tasks using the same trained joint degrees of freedom.