Labyrinthine Control of Upright Standing Posture

Abstract

Time series analysis of the vestibulospinal system with a 5-dimensional feedback model, an electromyographical study of sural muscle activity induced by galvanic stimulation of the labyrinth, and examination of labyrinthine postural response modulated by head position were performed to clarify the role the labyrinth in regulating upright standing posture. The analysis of body sway in standing posture showed that the vestibulospinal system regulates body sways of low frequency but the extent of the contribution of the vestibulospinal system is low in the overall control of standing posture. On examination of labyrinthine evoked EMGs, cathodal stimulation of the labyrinth induced a facilitation of the soleus muscle on the ipsilateral side and an inhibition of the soleus muscle on the contralateral side. These results indicated that the major role of the labyrinth in standing posture regulation was inhibitory control upon the extension of the contralateral leg rather than facilitatory influence on the extensor of the ipsilateral leg. Direction of body sway and leg muscle activity induced by galvanic labyrinthine stimulation were affected by neck torsion. The result indicates that the labyrinthine system produces the spinal reflex after processing information transmitted from the neck proprioceptor. © 1986, The Society of Practical Otolaryngology. All rights reserved.