Biomedical Engineering Reference
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surrounding wall with their extended hand such that it was passively rotated around
their shoulder joint, compelling arthrokinetic circular vection in the direction oppo-
site to the arm movement occurred. Illusory self-rotation occurred within 1-3 s and
was indistinguishable from actual self-motion. Arthrokinetic vection was accom-
panied by arthrokinetic nystagmus and resulted in considerable after-effects [ 24 ].
remarked that “actively pedaling the free wheeling floor while seated or turning the
railing with a hand-over-hand motion makes the experience very powerful” (p. 766).
We are currently investigating the feasibility of such a circular walking paradigm for
rotational self-motion simulation in VR ( http://iSpaceLab.com/iSpaceMecha ) .
2.4 Interaction of Walking and Other Modalities for Vection
2.4.1 Walking and Auditory Cues
While both biomechanical and visual cues can induce compelling vection, moving
auditory cues can elicit self-motion illusions only in 1/4-3/4 of participants, and
such auditory vection is much weaker, less compelling, and only occurs when partic-
ipants are blindfolded (for reviews, see [ 95 , 118 ]). Despite their low vection-inducing
potential, however, moving auditory cues have recently been shown to significantly
enhance visually induced vection [ 88 , 118 ] as well as biomechanically induced
circular vection [ 86 ]. In the latter study, participants were blindfolded and seated
stationary above the center of a circular treadmill. Auditory circular vection was
induced by binaural recordings of rotating sound fields presented via headphones
(Fig. 2.1 b), and biomechanical circular vection was induced by stepping along the
floor disc that rotated at the same velocity (60 /s) as the auditory stimulus (Fig. 2.1 c).
Although auditory vection by itself was weak and occurred in less than half of the
trials, adding rotating sound fields significantly enhanced biomechanically-induced
vection. Moreover, there were synergistic, super-additive effects when combining
auditory and biomechanical vection-inducing stimuli, in that bi-modal stimulation
resulted in vection intensities and perceived rotation realism that was higher than the
sum of the uni-modal vection ratings. This corroborates the importance of consistent
multi-modal simulation and suggests that even a fairly weak stimulus can sometimes
make a significant contribution. This is also promising from an applied perspective
of improving VR simulations, as sound spatialization can be of high fidelity while
still being affordable and technically feasible.
2.4.2 Walking and Visual Cues
2.4.2.1 Circular Vection
Lackner and DiZio [ 55 ] used a circular treadmill inside an optokinetic drum to
demonstrate that visual cues that did not match treadmill (i.e., walking) speed
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