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Slower velocity perception with stronger optokinetic nystagmus: A paradoxical perception in virtual reality


Background

Optokinetic nystagmus (OKN) was studied in an immersive virtual reality (VR) environment
with both typical optokinetic stimulation (OKs) wherein the head-tracking is active
(similar to be sitting in front of a rotating drum) or a unique stimulus (VR-OKs)
wherein the head-tracking is turned off, so head movements do not update the visual
image (which moves with the head).

Objective

To study both the perception of the stimulus velocity and eye movements while subjects
rotated their head from side to side and the visual scene was either a typical OKs
or VR-OKs.

Methods

9 healthy participants (aged 23 ± 2.4 y/o) had head and eye movements recorded under
typical OKs and VR-OKS while smoothly rotating their head horizontally from side to
side. Stimulation was delivered using a virtual reality setup on top of an eye movements
recording system.

Results

Under VR-OKs participants perceived faster stimulus velocity when the head and stimulus
had the same direction as compared to the head and stimulus in opposite directions.
When the head turned in the same direction as the stimulus, there were fewer fast
phase eye movements than when it rotated counter to stimulus motion direction. Conversely,
with typical OKs, participants perceived faster stimulus velocity when the head and
stimulus had opposite directions as compared to the head and stimulus having the same
direction.

Conclusions

The seemingly paradoxical results in which slower stimulus velocity is perceived in
tandem with stronger nystagmus can be explained by the simultaneous activation of
the Vestibulo-Ocular Reflex and OKN in accordance with the various visual and vestibular
stimuli.



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