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Chéla Willey, Zili Liu; Multimodal Contributions to Subjective Visual Vertical. Journal of Vision 2017;17(10):356. doi: 10.1167/17.10.356.
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We investigated the perception of subjective visual vertical (SVV) as a result of visuo-vestibuo-proprioceptive integration. Estimates of vertical are typically made by rotating a rod in space to a vertical position while standing upright. The visual context in which the rod is presented can influence SVV estimates as follows. In the rod and frame task, SVV estimates are biased towards the orientation of a surrounding contextual frame. However, SVV may also be influenced by vestibular and proprioceptive input indicating the direction of gravity. We sought to measure the effect of these modalities in SVV estimates by reducing their contribution in four conditions. Participants performed the rod and frame task while standing upright and while lying down using a virtual reality headset. This allowed us to eliminate contributing information due to vestibular gravitational cues available in the upright position. The use of virtual reality also allowed for the immersed visual illusion of the upright position in the supine condition. Further, we manipulated proprioceptive input by applying vibration to the participants' back in the supine position, the feet in the upright position and to the neck in both positions during half of the trials in each body orientation condition. During repeated trials, participants judged the orientation (clockwise or counterclockwise) of the rod located at the center of a neutral or rotated 3D frame. We found that there was an increase in bias towards the orientation of the frame and a decrease in sensitivity in SVV estimates in the supine conditions as compared to upright conditions, suggesting an effect of vestibular information. However, we found limited support that proprioceptive information (without vibration) influenced SVV estimates in the current study. Our results suggest that SVV estimates are more heavily influenced by visual cues when there is a lack of available vestibular cues.
Meeting abstract presented at VSS 2017
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