Experimental Brain Research

, Volume 174, Issue 4, pp 701–711

Modulation of muscle sympathetic bursts by sinusoidal galvanic vestibular stimulation in human subjects

  • Leah R. Bent
  • Philip S. Bolton
  • Vaughan G. Macefield
Research Article

DOI: 10.1007/s00221-006-0515-6

Cite this article as:
Bent, L.R., Bolton, P.S. & Macefield, V.G. Exp Brain Res (2006) 174: 701. doi:10.1007/s00221-006-0515-6

Abstract

There is controversy as to whether the vestibulosympathetic reflexes demonstrated in experimental animals actually exist in human subjects. While head-down neck flexion and off-vertical axis rotation can increase muscle sympathetic nerve activity (MSNA) in awake subjects, we recently showed that bipolar galvanic vestibular stimulation (GVS) does not. However, it is possible that our stimuli (2 mA, 1 s)—although capable of causing strong postural and occulomotor responses—were too brief. To address this issue we activated vestibular afferents using continuous sinusoidal (0.5–0.8 Hz, 60–100 cycles, ±2 mA) bipolar binaural GVS in 11 seated subjects. Sinusoidal GVS evoked robust vestibular illusions of “rocking in a boat” or “swinging from side to side.” Cross-correlation analysis revealed a cyclic modulation of MSNA ranging from 31 to 86% across subjects (mean ± SE 58 ± 5%), with total MSNA increasing by 156 ± 19% (P = 0.001). Furthermore, we documented de novo synthesis of sympathetic bursts that were coupled to the sinusoidal input, such that two bursts—rather than the obligatory single burst—could be generated within a cardiac interval. This demonstrates that the human vestibular apparatus exerts a potent facilitatory influence on MSNA that potentially operates independently of the baroreceptor system.

Keywords

VestibulosympatheticPostureAutonomicCardiovascularOrthostatic hypotension

Copyright information

© Springer-Verlag 2006

Authors and Affiliations

  • Leah R. Bent
    • 1
  • Philip S. Bolton
    • 2
  • Vaughan G. Macefield
    • 3
  1. 1.Department of Human Health and Nutritional SciencesUniversity of GuelphGuelphCanada
  2. 2.School of Biomedical Science, Faculty of HealthUniversity of NewcastleCallaghanAustralia
  3. 3.Prince of Wales Medical Research InstituteUniversity of New South WalesSydneyAustralia