The role of multiple contralesional motor areas for complex hand movements after internal capsular lesion

Abstract

Imaging techniques document enhanced activity in multiple motor areas of the damaged and contralesional (intact) hemisphere (CON-H) after stroke. In the subacute stage, increased activity within motor areas in the CON-H during simple movements of the affected hand has been shown to correlate with poorer motor outcome. For those patients in the chronic stage who recovered well, the functional relevance of an increased activation within the CON-H is unclear. Using trains of repetitive transcranial magnetic stimulation (TMS) during performance of complex finger movements, we tested the behavioral relevance of regional functional magnetic resonance imaging (fMRI) activation within the CON-H for sequential finger movement performance of the recovered hand in seven patients who had experienced a subcortical stroke. TMS was navigated over fMRI activation maxima within anatomically preselected regions of the CON-H, and effects were compared with those of healthy controls. Stimulation over the dorsal premotor cortex (dPMC), the primary motor cortex (M1), and the superior parietal lobe (SPL) resulted in significant interference with recovered performance in patients. Interference with the dPMC and M1 induced timing errors only, SPL stimulation caused both timing and accuracy deficits. The present results argue for a persistent beneficial role of the dPMC, M1, and SPL of the CON-H on some aspects of effectively recovered complex motor behavior after subcortical stroke.

Figures

Figure 1.

A, Subcortical lesions of the patients all flipped to the right side and are marked with a red cycle. The average T1 image (right) shows the lesion in the posterior internal capsule at group level. B, fMRI results for each patient during performing the finger sequence with their formerly impaired hand; only the CON-H is shown for each patient. The right activation map (smoothed for overlay with 6 mm) shows the group effect of all patients for the CON-H (left) and the DAM-H (right) projected on the segmented T1 anatomy Montreal Neurological Institute reference brain. Note the interindividual variability of activation maxima within the precentral gyrus.

Figure 2.

Setting during the experimental paradigm during the TMS experiment. Navigation within different functional representation sites demonstrated in one subject during complex finger sequence performance coded by numbers is shown.

Figure 3.

Rating of aversiveness (light gray) and disruptiveness (dark gray) of the stimuli. All stimuli were more aversive and disruptive than SHAM stimuli. Within the control stimuli, the FRO stimuli were more aversive and disruptive than all of the PERI stimuli. Other comparisons did not show significant differences. VAS, Visual analog scale. *p < 0.05; ***p < 0.001.

Figure 4.

Differences in performance on temporal accuracy; delay from 1000 ms (= 0) after TMS jamming compared with baseline for patients (stroke) and HCs and patients minus HCs. All “verum stimuli” over the CON-H (M1, PMC, and SPL) showed a significant effect selectively for the stroke patients. Control stimuli (SHAM, 90° upright coil; FRO and PERI over lower arm flexors) showed no differential effect between subject groups.