ABSTRACT
Background: It is well documented in limb motor research that providing the optimal practice and feedback conditions can have positive outcomes for the learning of new movements. However, it remains unclear if the training conditions used for limb movements can be directly applied to the speech motor system of healthy adults and individuals with acquired motor speech disorders. Collectively these practice and feedback conditions are known as the principles of motor learning (PML), and they have recently been applied to the rehabilitation of motor speech disorders with promising results.
Aims: The purpose of this systematic review is to identify which PML have been examined in the speech motor learning literature, to determine the effectiveness of these principles, and to ascertain future lines of research.
Methods & Procedures: A systematic search of the literature was completed that involved the combination of a primary search term with a secondary search term. All articles were independently reviewed and scored by the first two authors. To guide the selection process strict inclusion and exclusion criteria were implemented. Additionally, authors used a 15-category evidence-rating system to judge the overall quality of each study. After the study was scored, points were totalled into an overall quality rating of high, intermediate, or low with respect to methodological rigour and interpretability.
Outcomes & Results: Seven articles met inclusion criteria, including three randomised controlled trials and four single-participant designs. Five of the articles focused on motor speech disorders, including investigations of apraxia of speech (four studies) and hypokinetic dysarthria from Parkinson's disease (one study), while two studies focused on speech motor performance in healthy adults. Five of the articles were judged to be of high quality while two were judged to be of intermediate quality.
Conclusions: Although limited, the current level of evidence for the application of the PML to speech motor learning in both healthy adults and individuals with motor speech disorders is promising and continued investigation is warranted.
