Creating a spinning sensation in stationary observers: insights for visual-vestibular sensory integration

BY Ramy Kirollos

Our sensory organs (e.g. eyes, ears, nose) are the means by which the brain receives input about the world and converts this to meaningful experience. Because of the differing properties of our sensory organs, information from these various sources can sometimes be in conflict. So how does the brain deal with conflicting sensory information? This is exactly the question we sought to answer in a recent paper from my PhD work.

We examined what happens when the information from the visual system indicates that a person is not moving but the vestibular organs in the inner ear responsible for balance conflictingly indicate that a person is moving. Would the brain prioritize visual information and determine that the individual is stationary? Or would balance cues to motion be too strong to ignore? Alternatively, would the brain negotiate a compromise to make sense of this conflicting information on whether a person is moving? These were all plausible outcomes going into the experiment.

Figure: Woman Wearing White Virtual Reality Goggles - Credit to http://homedust.com/" by Homedust is licensed under CC BY 2.0.

In our experiment, participants received caloric vestibular stimulation to stimulate the balance system and cool the endolymph fluid in the vestibular organs responsible for sensing motion in the yaw axis, creating a spinning sensation. Participants wore a virtual reality headset and observed a stationary vertical stripe pattern at the same time. The stationary display in virtual reality coupled with the caloric vestibular stimulation signaling motion created a visual-balance, or visual-vestibular conflict. Participants indicated their direction, speed and duration of any perceived spinning with a knob. We found that the visual-vestibular conflict produced slower and shorter spinning experiences compared to another condition where participants only received caloric vestibular stimulation without any conflicting visual cues (eyes closed). These findings led us to conclude that rather than one sensory system dominating perception during conflict, the brain appears to weigh incoming cues based on their reliability and integrates them in a statistically optimal fashion.

The findings of this experiment are important because most research investigating visual-vestibular integration use visual cues to produce a self-motion experience in the absence of balance cues, or use mechanical motion systems to displace the individual as a means to provide balance cues. Using caloric vestibular stimulation to stimulate the balance system as done in our experiment is a unique method that can deliver new insights in understanding visual-vestibular sensory integration.

Why does this matter? There is still confusion on the value of integrating balance cueing for training in applications like flight and vehicle simulation. Our findings demonstrate the visual system does not simply dominate or override other sensory information. Future research on visual-vestibular integration building on our results can have important implications for the integration of new balance cueing methods in flight and vehicle simulation.

Read the details of our findings and the unique methodologies used in our prize-winning paper below.