Abstract
There are aging- and stroke-induced changes on sensorimotor control in daily activities, but their mechanisms have not been well investigated. This study explored speed-, aging-, and stroke-induced changes on sensorimotor control. Eleven stroke patients (affected sides and unaffected sides) and 20 control subjects (10 young and 10 age-matched individuals) were enrolled to perform elbow tracking tasks using sinusoidal trajectories, which included 6 target speeds (15.7, 31.4, 47.1, 62.8, 78.5, and 94.2 deg/s). The actual elbow angle was recorded and displayed on a screen as visual feedback, and three indicators, the root mean square error (RMSE), normalized integrated jerk (NIJ) and integral of the power spectrum density of normalized speed (IPNS), were used to investigate the strategy of sensorimotor control. Both NIJ and IPNS had significant differences among the four groups (P<0.01), and the values were ranked in the following order: young controls < age-matched controls <unaffected sides of stroke patients <affected sides of stroke patients, which could be explained by the stroke- and aging-induced increase in reliance on feedback control. The RMSE increased with the increase in the target speed and the NIJ and IPNS initially declined and then remained steady for all four groups, which indicated a shift from feedback to feedforward control as the target speed increased. The feedback-feedforward trade-off induced by stroke, aging and speed might be explained by a change in the transmission delay and neuromotor noise. The findings in this study improve our understanding of the mechanism underlying the sensorimotor control and neurological changes caused by stroke and aging.
Highlights
Target-directed arm movements are essential components of people’s daily activities, which usually require high levels of motion speed and accuracy [1,2]
The actual elbow angle was recorded and displayed on a screen as visual feedback, and three indicators, the root mean square error (RMSE), normalized integrated jerk (NIJ) and integral of the power spectrum density of normalized speed (IPNS), were used to investigate the strategy of sensorimotor control. Both NIJ and IPNS had significant differences among the four groups (P
The purpose of this study focused on how stroke and aging influence sensorimotor control, and we selected a series of elbow tracking tasks with 6 uniformly changing speeds, which was performed by stroke patients and healthy subjects
Summary
Target-directed arm movements are essential components of people’s daily activities, which usually require high levels of motion speed and accuracy [1,2]. Most optimal motor behaviors reflect a combination of two interacting strategies, feedback and feedforward control, while target-directed arm movements belong to this category [4]. Feedback control is an essential cognitive and motor skill for people to optimize motor performance, which refers to a modification of movement with the sensory information, involving error detection and correction during target-directed movements. This control strategy can contribute to a high degree of terminal accuracy, but it needs to account for the feedback loop delay [5]. Many researchers have suggested that there is a hybrid of feedback and feedforward control rather than isolated feedback or feedforward sensorimotor control of human movements [6,7,8,9]
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