Abstract
The vestibulo-ocular reflex (VOR) plays an important role in controlling the gaze at a visual target. Although patients with vestibular hypofunction aim to improve their VOR function, some retain dysfunction for a long time. Previous studies have explored the effects of direct current stimulation on vestibular function; however, the effects of random noise stimulation on eye–head coordination have not previously been tested. Therefore, we aimed to clarify the effects of high frequency noisy vestibular stimulation (HF-nVS) on eye–head coordination related to VOR function. Thirteen healthy young adult participants with no serious disease took part in our study. The current amplitude and density used were 0.4 mA and 0.2 mA/cm2, respectively, with a random noise frequency of 100–640 Hz. The electrodes were located on both mastoid processes. The stimulus duration and fade in/out duration were 600 and 10 s, respectively. Subjects oscillated their head horizontally, gazing at the fixation point, at 1 Hz (0.5 cycles/s) for 30 repetitions. The coordination of eye–head movements was measured by eye-tracking and a motion capture system. Peak-to-peak angles for eye and head movement and deviation of the visual line from the fixation target revealed no significant differences between HF-nVS and sham. The lag time between the eye and head movement with HF-nVS post-stimulation was significantly shorter than that of the sham. We found that HF-nVS can reduce the lag time between eye and head movement and improve coordination, contributing to a clear retinal image. This technique could be applied as a form of VOR training for patients with vestibular hypofunction.
Highlights
When we look at an object in the world around us, eye–head coordination is vital to accurately identifying that object
Forbes et al (2020) demonstrated that vestibular afferents were sensitive to alternating currents ranging randomly between low and high frequencies (0–300 Hz) known as Noisy Vestibular Stimulation, and the neck motor neurons were activated by vestibular stimulation
To test the hypothesis that high frequency noisy vestibular stimulation (HF-nVS) should decrease the deviation from the fixation target and the time lag between the eye and head motions, we measured changes in eye–head coordination related to the vestibulo-ocular reflex (VOR) function
Summary
When we look at an object in the world around us, eye–head coordination is vital to accurately identifying that object. Several previous studies applied a small direct current to the right and left mastoid processes behind the ear, and the firing rate of all vestibular afferents could be modified by the current (Fitzpatrick and Day, 2004; Uchino and Kushiro, 2011; Yang et al, 2015). The vestibular afferents were activated in response to high frequency noisy stimulation (Forbes et al, 2020) These results implied that the noise vestibular stimulation at high frequency might affect human behavior, mainly influenced by the vestibula
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