Quantification of Vestibulospinal Reflex Under the Stress Condition on Both Soleus Muscles
Research in Vestibular Science
Research in Vestibular Science, Vol.11(1) : 14~22, 2012
Background and Objectives : Vestibulospinal reflex (VSR), which is measured in static state, tends to be compensated prior to vestibul-ospinal reflex. Therefore, by establishing method that enables to track and observe quantified VSR, the reliability of experiment is attempted to be increased.
Materials and Methods : On five SD Rats to measure electromyogram (EMG), electrodes, in the form of stranded cables composed of seven wires, are chronically implanted on both sides of the soleus muscles. Pre and post operative condition of sitting still, standing, and ladder step walking was compared before, and six and twenty four hours after a unilateral labyrinthectomy with quantified muscle activity in maximal voluntary activity. Simultaneously by using multi modality electric potential plus package, the muscle activity between the two legs was tracked and compared.
Results: In the sitting still position, the left/right soleus muscle activities were 25.7/26.0 μV before a unilateral labyrinthectomy which was changed after the surgery with the value of 23.1/8.1 μV and 23.4/14.3 μV when six and twenty four hours passed respectively. In the standing position, 92.8/124.0 μV of preoperative value was changed to 89.6/37.3 μV six hours after the unilateral labyrinthectomy, and it was 97.0/54.7 μV 24 hours after. The preoperative value in ladder step walking test was 56.2/86.0 μV, and postoperative ones were 54.9/21.2 μV and 55.7/38.0 μV after six and twenty four hours respectively.
Conclusion: VSR assessment method by using quantitative EMG well reflects the process of vestibular compensation, and to maintain the tension of extensor muscles, ladder step walking test is shown to be useful.