Quantification of Vestibulospinal Reflex Under the Stress Condition on Both Soleus Muscles

Kim, Mi Joo; Jang, Seo Jin; Lee, Eun Ji; Yu, Ah Ram; Hwang, Jong Hyun; Han, Gyu Cheol; Lee, Ju Kang

Abstract

BACKGROUND AND OBJECTIVES
Vestibulospinal reflex (VSR), which is measured in static state, tends to be compensated prior to vestibule-ocular 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 microV before a unilateral labyrinthectomy which was changed after the surgery with the value of 23.1/8.1 microV and 23.4/14.3 microV when six and twenty four hours passed respectively. In the standing position, 92.8/124.0 microV of preoperative value was changed to 89.6/37.3 microV six hours after the unilateral labyrinthectomy, and it was 97.0/54.7 microV 24 hours after. The preoperative value in ladder step walking test was 56.2/86.0 microV, and postoperative ones were 54.9/21.2 microV and 55.7/38.0 microV 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.