title: Interaction effects of galvanic vestibular stimulation and head position on the soleus H reflex in humans.
abstract: OBJECTIVE
  The objective of this study is to measure the influence of galvanic vestibular stimulation and head-on-body alignment on the soleus H-reflex in prone human subjects.
  
  
  METHODS
  We studied changes in the amplitude of the right soleus H-reflex to monopolar monaural galvanic stimulation in 10 healthy prone lying subjects. Trials were randomly administered according to head position (left or right) and stimulus polarity (anode or cathode). We also investigated the influence of the conditioning stimuli by examining the amplitude of the H-reflex based on head position without galvanic stimulation. A one-way and two-way repeated measures analysis of variance were used to compare the mean amplitudes of the test and conditioned H-reflexes.
  
  
  RESULTS
  The greatest facilitation was observed when the head was turned to the left and coupled with cathodal stimulation. The largest inhibitory effect was found when the head was turned to the right and paired with anodal stimulation. However, when head left was paired with anodal stimulation or head right was coupled with cathodal stimulation, only minimal changes in amplitude were observed.
  
  
  CONCLUSIONS
  The results demonstrate that there is an interaction between head position and galvanic stimulus polarity when measuring the excitability of the soleus motoneuron pool in prone lying subjects.
authors.affiliation: School of Human Kinetics, The University of British Columbia, Vancouver, BC, Canada.
authors.forename: Paul M
authors.initials: PM
authors.lastname: Kennedy
authors.forename: J Timothy
authors.initials: JT
authors.lastname: Inglis
mesh_terms: D000328:Adult; D004558:Electric Stimulation; D004566:Electrodes; D007839:Functional Laterality / Q000502:physiology; D006181:H-Reflex / Q000502:physiology*; D019416:Head Movements / Q000502:physiology*; D006801:Humans; D008297:Male; D009046:Motor Neurons / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D016684:Prone Position / Q000502:physiology; D014722:Vestibule, Labyrinth / Q000502:physiology*