Alterations of Vestibuloocular Reflex and Heart Rate Variability by Sinusoidal Rotation in Adults

ABSTRACT

BACKGROUND: The nature of the interactions between the vestibular and autonomic systems is complex and has not been fully defined. The vestibuloocular reflex induced by sinusoidal rotation and the activity of the autonomic nerves in the heart were measured to investigate the interactions between the vestibular system and the autonomic nervous system in healthy adults. METHODS: Eye movements induced by sinusoidal rotation of the whole body or optokinetic stimulation at 0.04 Hz were analyzed in regards to their gain, phase, and symmetry. EKG was measured during vestibular stimulation and analyzed in heart rate variabilities including mean R-R interval, standard deviation (SD) and coefficient of variance (CV) of R-R interval, and power spectrum of the low frequency region (LF) and high fre-quency region (HF). RESULTS: The gain of eye movement was 0.65 degree +/-0.03 by rotatory stimulation and 0.70 degree +/-0 . 0 2 by optokinetic stimulation. The gain of visual suppression was 0.08 degree +/-0.02, which was a significant decrease com-pared with the rotatory stimulation, and visual enhancement increased the gain significantly, 0.84 degree +/-0.04 (p<0.01). In the R-R interval, the resting condition (control) was 0.82 degree +/-0.03 sec. Rotatory and optokinetic stimulations did not show any significant differences compared with the control, however, visual suppression showed a significant increase and visual enhancement showed a significant decrease (p<0.01). CV was 0.06 degree +/-0.02 in the control and visual enhancement increased significantly (p<0.05). In LF/HF the control was 1.40 degree +/-0.23, which was not different from the rotatory or optokinetic stimulation. However, visual suppression decreased the LF/HF significantly and visual enhancement increased the LF/HF significantly compared with the control (p<0.01). CONCLUSIONS: These results suggest that the degree of gain corresponds with LF/HF and that increased gain in visual enhancement is related to the activity of the sympathetic nerves.