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. 2007 Aug;130(Pt 8):2146-58.
doi: 10.1093/brain/awm145. Epub 2007 Jul 11.

Ipsilesional Motor Deficits Following Stroke Reflect Hemispheric Specializations for Movement Control

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Free PMC article

Ipsilesional Motor Deficits Following Stroke Reflect Hemispheric Specializations for Movement Control

Sydney Y Schaefer et al. Brain. .
Free PMC article

Abstract

Recent reports of functional impairment in the 'unaffected' limb of stroke patients have suggested that these deficits vary with the side of lesion. This not only supports the idea that the ipsilateral hemisphere contributes to arm movements, but also implies that such contributions are lateralized. We have previously suggested that the left and right hemispheres are specialized for controlling different features of movement. In reaching movements, the non-dominant arm appears better adapted for achieving accurate final positions and the dominant arm for specifying initial trajectory features, such as movement direction and peak acceleration. The purpose of this study was to determine whether different features of control could characterize ipsilesional motor deficits following stroke. Healthy control subjects and patients with either left- or right-hemisphere damage performed targeted single-joint elbow movements of different amplitudes in their ipsilateral hemispace. We predicted that left-hemisphere damage would produce deficits in specification of initial trajectory features, while right-hemisphere damage would produce deficits in final position accuracy. Consistent with our predictions, patients with left, but not right, hemisphere damage showed reduced modulation of acceleration amplitude. However, patients with right, but not left, hemisphere damage showed significantly larger errors in final position, which corresponded to reduced modulation of acceleration duration. Neither patient group differed from controls in terms of movement speed. Instead, the mechanisms by which speed was specified, through modulation of acceleration amplitude and modulation of acceleration duration, appeared to be differentially affected by left- and right-hemisphere damage. These findings support the idea that each hemisphere contributes differentially to the control of initial trajectory and final position, and that ipsilesional deficits following stroke reflect this lateralization in control.

Figures

Fig. 1
Fig. 1
Lesion locations based on tracing lesions from MRI or CT scans were superimposed on axial slices, separately for left-hemisphere-(displayed on left) and right-hemisphere-damaged (displayed on right) patients. Colors of shaded regions denote percentage (20, 40, 60, 80 or 100%) of left- and right-hemisphere-damaged patients with lesion in the corresponding area.
Fig. 2
Fig. 2
(A) Lateral and top view of experimental apparatus are shown. (B) Experimental task required movement of cursor from start circle to 1 of 2 target circles, with upper arm restrained.
Fig. 3
Fig. 3
(A) Final positions at movement end for each trial (dot) are displayed relative to gray targets for a representative subject from each experimental group. (B) Mean absolute final position error, mean variable final position error and movement time for each target is displayed for the left and right arms of control subjects and the ipsilesional arms of left- and right-hemisphere-damaged patients. Bars indicate standard error of mean.
Fig. 4
Fig. 4
(A) Average tangential velocity profiles for each target for representative control subjects and hemisphere-damaged patients. (B) Mean peak velocity for each target is displayed for the left and right arms of control subjects and the ipsilesional arms of left- and right-hemisphere-damaged patients. Bars indicate standard error of mean.
Fig. 5
Fig. 5
(A) Average tangential acceleration profiles for each target for representative control subjects and hemisphere-damaged patients. (B) Mean peak acceleration (normalized to% max) and acceleration duration for each target is displayed for the left and right arms of control subjects and the ipsilesional arms of left- and right-hemisphere-damaged patients. Bars indicate standard error of mean.
Fig. 6
Fig. 6
Mean peak deceleration (normalized to% min) and deceleration duration for each target is displayed for the left and right arms of control subjects and the ipsilesional arms of left- and right-hemisphere-damaged patients. Bars indicate standard error of mean.
Fig. 7
Fig. 7
Constant final position error (y axis) and acceleration duration (x axis) of each trial (dot) are displayed for representative control subjects and hemisphere-damaged patients. Final position error is signed, such that positive values indicate overshoot of target, and negative values indicate undershoot of target. Ellipses represent the 99% confidence interval of the data from each subject.

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