The Increase in Overlap of Cortical Activity Preceding Static Elbow/Shoulder Motor Tasks Is Associated With Limb Synergies in Severe Stroke.
Jun Yao, Julius P A Dewald
PMID 29890871WHAT IT FOUND
In severe chronic stroke, cortical activity for shoulder and elbow tasks became more overlapped before movement.
That overlap was associated with lower upper-limb motor scores and greater elbow torque coupling.
Key findings
01During motor preparation, cortical overlap between shoulder abduction and elbow flexion increased over time in severely impaired stroke, but decreased in controls and moderately impaired stroke.
02The increasing overlap was associated with lower UE-FMA scores and higher torque coupling ratio during elbow flexion.
03Severely impaired stroke showed larger cortical overlap near movement onset than moderately impaired stroke and control groups.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
Only 21 subjects were studied, and subjects with cortical lesion were excluded, so the findings may not apply to all stroke survivors. The study reports associations, not proof that cortical overlap causes loss of independent joint control. Attention level and involvement of additional muscles remained possible confounding factors. The preliminary check of attention and additional muscles used only control subjects, so it does not fully rule out those effects. The findings are limited to shoulder and elbow flexion synergy, not wrist, finger, or extension synergy. No intervention was tested, so the paper does not show how to change therapy.
Declared interests
The supplied metadata says the work was supported by extramural NIH research. No author competing interests are reported in the supplied text.
The easy way to misread this
Do not conclude that increasing cortical overlap causes limb synergies or that a treatment should target it. The study found associations in a small sample and did not test an intervention.