Abstract
Stroke results in reorganization of residual brain networks. The functional role of brain regions within these networks remains unclear, particularly those in the contralesional hemisphere. We studied 25 stroke patients with a range of motor impairment and 23 healthy age-matched controls using magnetoencephalography (MEG) and electromyography (EMG) to measure oscillatory signals from the brain and affected muscles simultaneously during a simple isometric hand grip, from which cortico-muscular coherence (CMC) was calculated. Peaks of cortico-muscular coherence in both the beta and gamma bands were found in the contralateral sensorimotor cortex in all healthy controls, but were more widespread in stroke patients, including some peaks found in the contralesional hemisphere (7 patients for beta coherence and 5 for gamma coherence). Neither the coherence value nor the distance of the coherence peak from the mean of controls correlated with impairment. Peak CMC in the contralesional hemisphere was found not only in some highly impaired patients, but also in some patients with good functional recovery. Our results provide evidence that a wide range of cortical brain regions, including some in the contralesional hemisphere, may have influence over EMG activity in the affected muscles after stroke thereby supporting functional recovery.
Highlights
After stroke, both functional magnetic resonance imaging and electroencephalography (EEG) studies have demonstrated alterations in brain activity during movement of the affected hand, in the contralesional hemisphere (Ward et al, 2003; Serrien et al, 2004; Gerloff et al, 2006a; Cramer, 2008)
The most widespread changes are seen in those patients with more impairment and it is still unclear whether new task related brain activity, within the contralesional hemisphere, is supporting or hindering recovered motor function
Et al, 2002; Fridman et al, 2004; Lotze et al, 2006). Evidence of the latter comes from the finding that contralesional primary motor cortex (M1) in chronic stroke patients maintains an inhibitory influence over ipsilesional M1 during both movement preparation and execution (Murase et al, 2004)
Summary
Both functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) studies have demonstrated alterations in brain activity during movement of the affected hand, in the contralesional hemisphere (Ward et al, 2003; Serrien et al, 2004; Gerloff et al, 2006a; Cramer, 2008). The most widespread changes are seen in those patients with more impairment and it is still unclear whether new task related brain activity, within the contralesional hemisphere, is supporting or hindering recovered motor function Evidence of the former is provided by studies in which single pulse transcranial magnetic stimulation (TMS) to dorsal premotor cortices in either hemisphere disrupted motor performance in chronic stroke patients but not in control subjects Et al, 2002; Fridman et al, 2004; Lotze et al, 2006) Evidence of the latter comes from the finding that contralesional primary motor cortex (M1) in chronic stroke patients maintains an inhibitory influence over ipsilesional M1 during both movement preparation and execution (Murase et al, 2004). The results have been mixed, raising the possibility that contralesional cortical motor regions contribute to motor recovery in some but not all stroke patients
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