AUTHOR=Nguyen Thanh Tin , Kang Jin-Ju , Oh Sun-Young 

TITLE=Thresholds for vestibular and cutaneous perception and oculomotor response induced by galvanic vestibular stimulation

JOURNAL=Frontiers in Neurology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/neurology/articles/10.3389/fneur.2022.955088

DOI=10.3389/fneur.2022.955088

ISSN=1664-2295

ABSTRACT=<sec><title>Objectives</title><p>In this study, the specific threshold intensities and response characteristics of galvanic vestibular stimulation (GVS) on vestibular (conscious) and cutaneous (detrimental) perception as well as oculomotor nystagmus (reflex) were determined.</p></sec><sec><title>Methods</title><p>The threshold intensities for vestibular and cutaneous perception and oculomotor response induced by GVS were determined in 25 right-handed healthy subjects (32.6 ± 7.2 years of age; 56% female). The subjects were seated upright, and eye movements were recorded while a direct GVS current was applied with paradigms of cathode on the right and anode on the left (CRAL) and also cathode on the left and anode on the right (CLAR).</p></sec><sec><title>Results</title><p>Subjects experienced dizziness, sense of spinning, or fall tendency, which was more frequently directed to the cathode (76%) than the anode (24%, <italic>p</italic> &lt; 0.001, chi-square one-variable test) at mean current greater than 0.98 ± 0.29 mA (mean vestibular threshold). The current also triggered a more frequent mild tingling sensation at the cathode (56%) than the anode (30%) or on both sides (14%; <italic>p</italic> = 0.001, chi-square one-variable test) when above the mean cutaneous threshold of 0.9 ± 0.29 mA. Above the mean oculomotor threshold of 1.61 ± 0.35 mA, combined horizontal and torsional nystagmus was more frequent toward the cathode (86%) than toward the anode (<italic>p</italic> &lt; 0.001, chi-square one-variable test). The mean oculomotor threshold was significantly higher than both the vestibular (<italic>p</italic> &lt; 0.001, Mann–Whitney <italic>U</italic>-test) and cutaneous (<italic>p</italic> &lt; 0.001, Mann–Whitney <italic>U</italic>-test) thresholds, which were comparable (<italic>p</italic> = 0.317, Mann–Whitney <italic>U</italic>-test). There was no significant disparity in these specific thresholds between the two GVS paradigms. The vestibular threshold was significantly higher in males than in females [1 (0.5–1.25) mA vs. 0.75 (0.625–1.125) mA, <italic>Z</italic> = −2.241, <italic>p</italic> = 0.025, Mann–Whitney <italic>U</italic>-test]. However, the thresholds of cutaneous perception and oculomotor response did not differ by sex.</p></sec><sec><title>Conclusion</title><p>The findings indicate that thresholds for vestibular and somatosensory perception are lower than the oculomotor threshold. Therefore, a strategy to reduce GVS current intensity to the level of vestibular or somatosensory perception threshold could elicit beneficial vestibular effects while avoiding undesirable effects such as oculomotor consequences.</p></sec>