Abstract
This study investigated how stroke’s hemispheric localization affects motor performance, spinal maps and muscle synergies while performing planar reaching with and without assistive or resistive forces. A lesion of the right hemisphere affected performance, reducing average speed and smoothness and augmenting lateral deviation in both arms. Instead, a lesion of the left hemisphere affected the aiming error, impairing the feedforward control of the ipsilesional arm. The structure of the muscle synergies had alterations dependent on the lesion side in both arms. The applied force fields reduced the differences in performance and in muscle activations between arms and among populations. These results support the hypotheses of hemispheric specialization in movement control and identify potential significant biomarkers for the design of more effective and personalized rehabilitation protocols.
Highlights
Stroke is a prevalent cause of motor impairments worldwide and its incidence continues to rise [1,2,3]
Stroke Subjects Had Different Performance than Controls and the Differences Depended on the Side of the Brain Lesion: A Lesion on the Right Hemisphere Determined Worse Performance in both Arms in Terms of Average Speed, Smoothness and Lateral Deviation of the Overall Trajectory
The difference between the motor performance of stroke subjects and controls was task-dependent for both the contralesional arm (interaction effect: pathology x task; average speed F(4,94) = 13.53, p < 0.001, smoothness index F(4,94) = 17.41, p = 0.02, 100-ms aiming error F(4,94) = 15.51, p = 0.03 and lateral deviation F(4,94) = 16.04, p = 0.004) and the ipsilesional arm (interaction effect: pathology x task; average speed F(4,94) = 10.25, p = 0.002, smoothness index F(4,94) = 12.72, p = 0.001, 100-ms aiming error F(4,94) = 15.64, p = 0.022 and lateral deviation F(4,94) = 12.27, p = 0.011)
Summary
Stroke is a prevalent cause of motor impairments worldwide and its incidence continues to rise [1,2,3]. The contralesional arm is often characterized by motor deficits, including: (i) loss of fine motor control and deficits in motor planning and sensorimotor integration [12]; (ii) kinematics and dynamics trajectory abnormalities [12]; (iii) abnormal joint torque patterns [13,14] and joints temporal coordination [15,16,17], especially between elbow flexion and shoulder horizontal adduction [16]. Stroke survivors compensate for these deficits with extensive use of the side of the body ipsilateral to the lesion [22]
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