Effect of auditory constraints on motor performance depends on stage of recovery post-stroke

Abstract

In order to develop evidence-based rehabilitation protocols post-stroke, one must first reconcile the vast heterogeneity in the post-stroke population and develop protocols to facilitate motor learning in the various subgroups. The main purpose of this study is to show that auditory constraints interact with the stage of recovery post-stroke to influence motor learning. We characterized the stages of upper limb recovery using task-based kinematic measures in 20 subjects with chronic hemiparesis. We used a bimanual wrist extension task, performed with a custom-made wrist trainer, to facilitate learning of wrist extension in the paretic hand under four auditory conditions: (1) without auditory cueing; (2) to non-musical happy sounds; (3) to self-selected music; and (4) to a metronome beat set at a comfortable tempo. Two bimanual trials (15 s each) were followed by one unimanual trial with the paretic hand over six cycles under each condition. Clinical metrics, wrist and arm kinematics, and electromyographic activity were recorded. Hierarchical cluster analysis with the Mahalanobis metric based on baseline speed and extent of wrist movement stratified subjects into three distinct groups, which reflected their stage of recovery: spastic paresis, spastic co-contraction, and minimal paresis. In spastic paresis, the metronome beat increased wrist extension, but also increased muscle co-activation across the wrist. In contrast, in spastic co-contraction, no auditory stimulation increased wrist extension and reduced co-activation. In minimal paresis, wrist extension did not improve under any condition. The results suggest that auditory task constraints interact with stage of recovery during motor learning after stroke, perhaps due to recruitment of distinct neural substrates over the course of recovery. The findings advance our understanding of the mechanisms of progression of motor recovery and lay the foundation for personalized treatment algorithms post-stroke.

Keywords: bimanual movements; cerebrovascular disorders; electromyography; motor learning/training; rehabilitation; task specificity; upper extremity.

Figure 1

Custom-made wrist extension trainer.

Figure 2

Mean Brunel Mood Scale scores at baseline and after listening to self-selected music. Error bars represent the standard error. *Represents statistically significant differences at p < 0.05.

Figure 3

Cluster dendrogram from hierarchical cluster analysis using the Mahalanobis metric based on speed and amplitude of wrist extension on the first trial with the paretic hand at baseline (without auditory stimulation). Three distinct groups emerged.

Figure 4

Group means computed for the first trial with the paretic hand. (A) Speed of wrist extension in degrees per second; (B) extent of wrist extension in degrees; (C) root mean square of wrist extensor muscle activation during wrist extension; (D) root mean square of wrist flexor muscle activation during wrist extension; (E) log of wrist co-activation computed as ratio of wrist flexor to extensor muscle activation. The blue bars represent the group with spastic paresis, which had the lowest Fugl-Meyer scores, the red bars represent the spastic co-contraction group with intermediate Fugl-Meyer scores, and the green bars represent the minimal paresis group, which had the highest Fugl-Meyer scores. Values for the non-paretic hand are shown in gray for reference. Error bars represent the standard error. *Represents differences between the three groups at p < 0.05, and ⁺represents differences between the three groups at p < 0.1.

Figure 5

Trendlines of wrist extension performance variables over six repeated trials with the paretic hand under each condition for the three groups: (A) spastic paresis (blue); (B) spastic co-contraction (red); (C) minimal paresis (green). The four conditions are represented by the different patterned lines.

Figure 6

The bars represent the mean slopes showing the effect of auditory stimulation on bimanual-to-unimanual learning for wrist extension performance variables in the three groups: (A) spastic paresis (blue); (B) spastic co-contraction (red); (C) minimal paresis (green). Error bars represent the standard error. **Represents differences between the three groups at p < 0.01, and *represents differences between the three groups at p < 0.05.