Improving Movement Automaticity and Dual-Task Performance in People with Stroke: A Change of Focus?

Scherder, E.J.A. [Promotor]Bennekom, C.A.M. van [Promotor]Kamp, G.J. van der [Copromotor]Houdijk, J.H.P. [Copromotor

External attentional focus enhances movement automatization: a comprehensive test of the constrained action hypothesis.

An external focus of attention has been shown to result in superior motor performance compared to an internal focus of attention. This study investigated whether this is due to enhanced levels of movement automatization, as predicted by the constrained action hypothesis (McNevin, Shea, & Wulf, 2003). Thirty healthy participants performed a cyclic one-leg extension-flexion task with both the dominant and non-dominant leg. Focus of attention was manipulated via instructions. The degree of automatization of movement was assessed by measuring dual task costs as well as movement execution parameters (i.e., EMG activity, movement fluency, and movement regularity). Results revealed that an external focus of attention led to significantly better motor performance (i.e., shorter movement duration) than an internal focus. Although dual task costs of the motor task did not differ as a function of attentional focus, cognitive dual task costs were significantly higher when attention was directed internally. An external focus of attention resulted in more fluent and more regular movement execution than an internal focus, whereas no differences were found concerning muscular activity. These results indicate that an external focus of attention results in more automatized movements than an internal focus and, therefore, provide support for the constrained action hypothesis. © 2013 Elsevier B.V

Visuomotor control of walking in Parkinson’s disease: Exploring possible links between conscious movement processing and freezing of gait

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordIntroduction Changes in visual attention have been argued to influence freezing of gait (FOG) in people with Parkinson’s Disease (PD). However, the specific visual search patterns of people with FOG pathology (PD + FOG) and potential underlying mechanisms are not well understood. The current study explored visual search behavior in PD + FOG while walking on a pathway featuring environmental features known to exacerbate FOG (e.g., narrow doorway and tripping hazards). Potential attentional underpinning mechanisms were also assessed, such as conscious movement processing. Methods Visual search behavior of twelve people with PD + FOG tested in ON-state (Mage = 74.3) and twelve age-matched healthy controls (Mage = 72.5) were analysed during a complex walking task. The task required participants to step over an obstacle and navigate through a narrow doorway, surrounded by clutter. Results People with PD + FOG more frequently directed visual attention to ongoing and imminent steps compared to healthy controls (Mdn = 26% vs Mdn = 14%, respectively; p = 0.042). Self-reported conscious movement processing was also significantly higher in people with PD+FOG. The one participant who froze during the walking task fixated the future trip hazard (obstacle, approximately 6 steps ahead) almost exclusively during freezing trials (i.e., 60-100% of the trial). In contrast, during ‘non-freeze’ trials, this participant increased the duration of fixations towards ongoing and imminent steps. Conclusion Results suggest that people with PD + FOG strongly monitor/control ongoing and immediately upcoming stepping movements. However, prolonged fixations towards threats to future movements might prevent people with PD + FOG from processing the visual information needed to do this, thereby provoke freezing episodes