Abstract
Predictive control of movement is more efficient than feedback-based control, and is an important skill in everyday life. We tested whether the ability to predictively control movements of the upper arm is affected by age and by cognitive load. A total of 63 participants were tested in two experiments. In both experiments participants were seated, and controlled a cursor on a computer screen by flexing and extending their dominant arm. In Experiment 1, 20 young adults and 20 older adults were asked to continuously change the frequency of their horizontal arm movements, with the goal of inducing an abrupt switch between discrete movements (at low frequencies) and rhythmic movements (at high frequencies). We tested whether that change was performed based on a feed-forward (predictive) or on a feedback (reactive) control. In Experiment 2, 23 young adults performed the same task, while being exposed to a cognitive load half of the time via a serial subtraction task. We found that both aging and cognitive load diminished, on average, the ability of participants to predictively control their movements. Five older adults and one young adult under a cognitive load were not able to perform the switch between rhythmic and discrete movement (or vice versa). In Experiment 1, 40% of the older participants were able to predictively control their movements, compared with 70% in the young group. In Experiment 2, 48% of the participants were able to predictively control their movements with a cognitively loading task, compared with 70% in the no-load condition. The ability to predictively change a motor plan in anticipation of upcoming changes may be an important component in performing everyday functions, such as safe driving and avoiding falls.
Highlights
With aging, there is often a decline in some aspects of movement control, such as reaction time (Lodha et al, 2016) and explicit motor sequence learning (Bo et al, 2009)
There were 42 such trials in the older group, and seven such trials in the younger age group. These results suggest that for the older group switching from a rhythmic to a discrete movement type was more challenging than the reverse switch
Our goal was to study the effects of aging and of cognitive load on predictive control of movement
Summary
There is often a decline in some aspects of movement control, such as reaction time (Lodha et al, 2016) and explicit motor sequence learning (Bo et al, 2009). There are more postural preparation errors (Verrel et al, 2016), the incidence of falls increases (Fuller, 2000), and so does the variability in motor reactions (Lodha et al, 2016). Some of these “faults” in motor control stem from a difficulty in predicting upcoming changes in the environment that call for adjusting one’s motor plan (Levy-Tzedek et al, 2011b). Our first goal in the current study was to test the effects of age on the predictive control of movements.
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