Head roll dependent variability of subjective visual vertical and ocular counterroll.
We compared the variability of the subjective visual vertical (SVV) and static ocular counterroll (OCR), and hypothesized a correlation between the measurements because of their shared macular input. SVV and OCR were measured simultaneously in various whole-body roll positions [upright, 45 degrees right-ear down (RED), and 75 degrees RED] in six subjects. Gains of OCR were -0.18 (45 degrees RED) and -0.12 (75 degrees RED), whereas gains of compensation for body roll in the SVV task were -1.11 (45 degrees RED) and -0.96 (75 degrees RED). Normalized SVV and OCR variabilities were not significantly different (P > 0.05), i.e., both increased with increasing roll. Moreover, a significant correlation (R(2) = 0.80, slope = 0.29) between SVV and OCR variabilities was found. Whereas the gain of OCR is different from the gain of SVV, trial-to-trial variability of OCR follows the same roll-dependent modulation observed in SVV variability. We propose that the similarities in variability reflect a common otolith input, which, however, is subject to distinct central processing for determining the gain of SVV and OCR.
Department of Neurology, Zurich University Hospital, Zurich, Switzerland. alexander.tarnutzer@access.unizh.ch
Alexander A
AA
Tarnutzer
Christopher J
CJ
Bockisch
Dominik
D
Straumann
D000328:Adult; D005133:Eye Movements / Q000502:physiology*; D005260:Female; D018466:Gravity Sensing / Q000502:physiology; D019416:Head Movements / Q000502:physiology*; D006801:Humans; D007600:Judgment / Q000502:physiology; D008297:Male; D009949:Orientation / Q000502:physiology*; D010037:Otolithic Membrane / Q000502:physiology; D010775:Photic Stimulation; D011597:Psychomotor Performance / Q000502:physiology*; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology*; D012444:Saccule and Utricle / Q000502:physiology; D013028:Space Perception / Q000502:physiology; D014722:Vestibule, Labyrinth / Q000502:physiology*