The mechanism of physiological height vertigo. II. Posturography.

In order to validate the hypothesis that height vertigo is based on visual destabilization of free stance when the distance between eye and object becomes critically large, several of its consequences were demonstrated in posturographic experiments: (1) Visual signals conflicting with simultaneous vestibular and somatosensory inputs provided by sinusoidally tilting rooms may destabilize postural sway in the fore-aft as well as in the lateral direction. (2) In natural surrounding sway amplitudes increase with increasing eye-object distance up to 5 meters. Thus, teleologically, subjective height vertigo serves as an appropriate warning signal to withdraw the body from a stimulus situation inducing postural imbalance. (3) Postural height vertigo problems can be alleviated (a) by adjusting the head relative to the gravitational vector, and (b) by the presence of nearby stationary contrasts in the visual periphery according to the dominance of retinal periphery for dynamic spatial orientation.