Effect of Semicircular Canal Stimulation on the Perception of the Visual Vertical

Abstract

Herewith we investigate the influence of semicircular canal (SCC) stimulation on the SVV by rotating normal subjects in yaw about an earth-vertical axis, with velocity steps of Ϯ 90°/s, for 60 s. SVV was assessed by setting an illuminated line to perceived earth vertical in darkness, during a per-and postrotary period. Four head positions were tested: upright, 30°backward (chin up) or forward, and ϳ40°f orward from upright. During head upright/backward conditions, a significant SVV tilt (P Ͻ 0.01) in the direction opposite to rotation was found that reversed during postrotary responses. The rotationally induced SVV tilt had a time constant of decay of ϳ30 s. Rotation with the head 30°forward did not affect SVV, whereas the 40°forward tilt caused a direction reversal of SVV responses compared with head upright/backward. Spearman correlation values (Rho) between individual SCC efficiencies in different head positions and mean SVV tilts were 0.79 for posterior, 0.34 for anterior, and -0.80 for horizontal SCCs. Three-dimensional video-oculography showed that SVV and torsional eye position measurements were highly correlated (0.83) and in the direction opposite to the slow phase torsional vestibuloocular reflex. In conclusion: 1) during yaw axis rotation without reorientation of the head with respect to gravity, the SVV is influenced by SCC stimulation; 2) this effect is mediated by the vertical SCCs, particularly the posterior SCCs; 3) rotationally induced SVV changes are due to torsional ocular tilt; 4) SVV and ocular tilts occur in the "anticompensatory," fast phase direction of the torsional nystagmus; and 5) clinically, abnormal SVV tilts cannot be considered a specific indication of otolith system dysfunction.

Antihysteresis of perceived longitudinal body axis during continuous quasi-static whole-body rotation in the earth-vertical roll plane

“…We think that this reverse relation between torsional eye position and pLBA could be causal. As previously reported, ocular torsion induces changes of visual line settings and, thus, influences the perceived visual line orientation (Curthoys 1996;Mezey et al 2004;Pavlou et al 2003;Wade and Curthoys 1997). Wade and Curthoys (1997) In our experiments, static antihysteresis of pLBA was not only evident in upright whole-body roll positions, but also over the course of whole-body roll cycles.…”

“…Using verbal reports was not an option, as Van Beuzekom and Van Gisbergen (2000) had noted remarkably large random errors with this method, particularly for small whole-body tilts. It needs to be stressed, however, that the visual method is different from the verbal method, because the orientation of the projected luminous line on the retina can influence torsional eye position and the perception of body orientation in space (Curthoys 1996;Mezey et al 2004;Pavlou et al 2003;Wade and Curthoys 1997).…”

Relative diagnostic value of ocular vestibular evoked potentials and the subjective visual vertical during tilt and eccentric rotation

“…The similarity of the OVEMPs and the eccentric rotation error in our study suggests that in fact they are measuring similar functions. The remaining differences could be either because the tests rely on different sensors (vibration induced OVEMPs may be sensitive to saccule stimulation (Colebatch, 2010), and the visual vertical is influenced by semicircular canal stimulation directly (Pavlou, Wijnberg, 2003) or through changes in ocular torsion (Smith, Curthoys, 1995)), or perhaps the visual vertical is simply more variable owing to the requirement of active patient participation. OVEMPs are generally easier and cheaper to administer than eccentric rotation tests, and are more comfortable for the patient, making them an attractive component of comprehensive vestibular testing, along with air conducted sound CVEMPs, which predominately test the integrity of the saccule (Curthoys, 2010;McCue and Guinan, 1994), and the head impulse test, which can selectively test all 6 semi-circular canals (Cremer, Halmagyi, 1998).…”

Roll-Dependent Modulation of the Subjective Visual Vertical: Contributions of Head- and Trunk-Based Signals

“…These acceleration and deceleration values, however, are well above the detection threshold of the semicircular canals (0.05°/s 2 ; Diamond et al 1982; Shimazu and Precht 1965) and thus will lead to SCC stimulation during the turntable repositioning. Rotations with accelerations above the threshold of the SCC were found to modify errors in SVV (JaggiSchwarz and Hess 2003; Pavlou et al 2003). In a previous study with a similar protocol, we recorded three-dimensional eye movements using scleral search coils (Skalar, Delft, The Netherlands) to investigate possible postrotatory torsional nystagmus due to semicircular canal stimulation at the time of performing the SVV task (Tarnutzer et al 2009a).…”