Expectancy and affective response to challenging balance practice conditions in individuals with Parkinson's disease.

Psychological states can influence motor performance and learning. In Parkinson's disease (PD), placebo effects or expectancies for pharmacological treatment benefits are not uncommon, but little is known about whether self-efficacy, beliefs about personal performance capabilities, may play a role in this population. To address this question, we investigated whether experimental manipulations designed to enhance self-efficacy would benefit motor performance and learning in PD. A motor learning paradigm was utilized to determine the short-term (i.e., practice) and longer-term (i.e., retention) impact of self-efficacy enhancement when 44 individuals with PD (Hoehn and Yahr stage I-III) acquired a challenging balance skill. Using stratified randomization by Hoehn and Yahr stage, participants were assigned to a control group or one of two investigational groups: (a) an expectancy-relevant statement that encouraged an incremental mindset in which the balance skill, though initially challenging, was acquirable with practice (incremental theory group, IT), and (b) the expectancy-relevant statement in combination with a criterion for successful performance (incremental theory plus success criteria group, IT + SC). All groups improved their balance performance, but contrary to expectations, investigational groups did not outperform the control group at practice or retention. Unexpectedly, the IT + SC group reported greater nervousness than the control and IT groups, suggesting that the employed success criteria may have induced performance-related anxiety. Regression analyses revealed that self-efficacy increase from initial practice predicted performance at the end of practice and at retention. These findings highlight the potential contribution of psychological factors on motor function and rehabilitation in individuals with PD.