Background: Deficits in implicit motor sequence learning (IMSL) in individuals with Parkinson disease (PD) compared to age matched healthy controls (HC) are unclear.
Objective: The purpose of this paper is to present results of a systematic review with a meta-analysis examining the hypothesis that IMSL is impaired in individuals with PD when compared to HC.
Methods: Fifteen articles met our final criteria and assessed 299 individuals with PD and 244 HC. Raw mean and standard deviation data for the final block of repeated and final block of random practice trials were obtained to calculate sequence-specific learning (SSL) for individuals with PD and HC. Forest plots were used to depict the comparison of the groups by assessing standardized mean difference with random effect size.
Results: A significant and moderate effect size, 0.83 was found suggesting that individuals with PD demonstrated impaired SSL of motor sequences compared to HC.
Conclusions: Individuals with PD demonstrate a deficit compared with HC in their ability to implicitly learn motor tasks. Existing research lacks detail on the factors which may alter IMSL, either negatively or positively, such as the design features of current IMSL paradigms utilized and disease-specific characteristics. Successful motor rehabilitation of functional tasks in persons with PD is highly dependent on IMSL; therefore, an improved knowledge of the influence of these additional variables is critical.
Keywords: Implicit motor sequence learning; Parkinson disease.