Disturbances of Motoneurone Discharge in Muscles of Subjects with Hemiparetic Stroke
Following injury to the cerebrum or spinal cord, human subjects experience a cluster of clinical signs widely described as the “upper motoneurone syndrome”. This syndrome consists of “spasticity”, (which is an increase in muscle tone), muscular weakness, and disturbances in movement coordination. The mechanisms of muscular weakness have received relatively limited scrutiny. Hughlings Jackson (see Lassek, 1970) proposed that they resulted from a loss of net descending excitatory drive from cortical centres, and (in our view), this is quite likely to be a factor. However, it is also possible that changes in the pattern of motoneurone activation may occur following lesions to cortex or descending pathways, and that these changes may contribute to the disturbances in voluntary force generation, which include muscle weakness, increased effort and an exaggerated sense of fatigue.
KeywordsFiring Rate Motor Unit Joint Torque Contralateral Limb Motor Unit Recruitment
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