The production of voluntary movements is based on the functional integration between the cortical motor areas and the spinal circuits. The modalities and mechanisms for the conduction of the signals that descend from the cortex to the inter-neurons and motoneurons, are still the subject of debate. Recent studies show how the motor system can control muscle activation through a linear combination of muscle synergies, so as to reduce its redundancy and control difficulties.

Previous studies of the authors have shown that in a sample of subjects affected by stroke the muscular synergies were similar, during the execution of exercises in virtual reality (VRRS-EVO 4), for the number of affected limb and healthy limb, both in the same patient and between different patients, as well as in comparison with healthy subjects.

In order to assess whether the number of shared synergies between the healthy limb and the paretic limb was related to the size of the stroke and the functional outcomes of the lesion, was studied the relationship between the number of synergies with both the volume of the cerebral infarct was studied and with the values ​​of three functional scales. The only significant correlation found was that between shared synergies and manual dexterity function index, while correlations were not significant between muscle synergies and the remaining indices (imaging and 2 functional indices). The results seem to confirm the stability of the muscular synergies already observed with computational approaches and the possibility that the muscular synergies of more advanced functions are not found in the brainstem. However, it is necessary to repeat the observation in a larger number of patients to increase the robustness of the observation.