Dopa-Responsive Balance Changes Depend on Use of Internal Versus External Attentional Focus in Parkinson Disease

Background Parkinson disease (PD) impairs control of well-learned movements. Movement control improvements are found when individuals complete tasks while focusing attention externally on manipulating an object, which is argued to occur due to automatic processing associated with well-learned movements. Focusing attention internally (on movements of one's limbs) is believed to involve conscious control networks and hinders movement performance. Previous work has shown that an external focus of attention (EFA) improved postural stability in individuals with PD (compared with an internal focus of attention [IFA]), but this improvement occurred when patients were taking dopamine medication, which modulates basal ganglia functioning responsible for well-learned movements. Objective The purpose of this study was to determine whether an EFA or IFA is beneficial for postural stability in individuals with PD in the absence of dopamine replacement. Design A within-participant design was utilized. Methods Nineteen individuals with PD stood on a firm, unstable platform in 3 attentional conditions: (1) EFA, (2) IFA, and (3) control (participant asked to stand still). Displacement and variability of anterior-posterior and medial-lateral postural sway were measured with a balance system for fall risk assessment. The protocol was completed both “on” and “off” (mininum 12-hour withdrawal of) dopaminergic medications. Results While off medications, anterior-posterior sway variability was significantly lower during an IFA compared with the EFA and control. Anterior-posterior sway displacement and variability were significantly lower during the IFA, when off medications were compared with IFA and EFA while on medications. Limitations There was no comparison with a healthy age-matched control group, and a safety harness was used due to task difficulty. Conclusions An EFA may recruit automatic processes that involve degenerated basal ganglia in PD, and absence of dopamine exacerbates dysfunction. Training with an EFA may improve upon these automatic processes in individuals with PD.