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Global perspective jitter enhances vection in both active and passive observers

Conference Paper


Abstract


  • Background. Unlike vision, the vestibular system is only able to detect accelerating self-motions (Lishman & Lee, 1973). Thus, many studies examining the visual perception of self-motion in physically stationary observers (vection) have presented passive radial optic flow simulating constant velocity linear self-motion - the aim being to maximize vection by minimizing visual-vestibular conflict. However, it has been found that adding horizontal or vertical perspective jitter/oscillation (similar to the effects of camera shake) to these radial flow patterns enhances vection induced in stationary subjects (Palmisano et al., 2000, 2003; 2007). This vection advantage cannot be explained by traditional conflict theories. In order to better understand the role that visual-vestibular sensory integration plays in self-motion perception we examined an active head movement scenario. Method. The computer generated visual self-motion stimulus consisted of 1536 random dots placed uniformly within a 3D spatial environment. Constant-velocity forward self-motion was simulated by moving the dots toward the camera viewpoint at a rate of 0.75 of the total depth between the near and far clipping planes for each second in time elapsed. A 120fps digital camera was used to acquire images of a small infrared headset fitted to the top of the participants head. The images pixels were analysed in real-time using custom software written in C++ to obtain linearised inter-aural head position in centimetres. Head position data were then transmitted to the 3D rendering application to update the camera position in-line with the participants changing head position (active jitter condition). Head position data were recorded to file and could be used without head tracking to reproduce active visual jitter during a subsequent condition where the head was stationary (passive jitter condition). Participants swayed side to side at the waist along the inter-aural axis to a metronome triggering an audible cue every 0.5 second. During these 1.0Hz lateral head oscillations, randomised 30-second trials were used to display either non-jittering optic flow or laterally oscillating optic flow synchronized with inter-aural head position. Ratings of the perceived strength of induced vection were obtained from seven participants. Results. Vection strength ratings obtained with active head oscillation and synchronized display jitter were significantly greater than those without display jitter. The vection ratings produced by passively viewing display jitter were also significantly great than the non-jittering controls, as reported by Palmisano et al. previously. Conclusion. These findings show that visual display jitter enhances vection in depth, both when passively viewed or when viewed under active control. The similarity in vection ratings between active and passive conditions suggests that the addition of synchronized input from the otoliths consistent with the pattern of optic-flow jitter did not enhance vection more than that reported with passively viewed jittering flow.

Publication Date


  • 2008

Citation


  • Kim, J. & Palmisano, S. A. (2008). Global perspective jitter enhances vection in both active and passive observers. XXV Barany Society Meeting Program and Abstracts (pp. 347-347). Kyoto, Japan: Barany Society.

Start Page


  • 347

End Page


  • 347

Place Of Publication


  • Kyoto, Japan

Abstract


  • Background. Unlike vision, the vestibular system is only able to detect accelerating self-motions (Lishman & Lee, 1973). Thus, many studies examining the visual perception of self-motion in physically stationary observers (vection) have presented passive radial optic flow simulating constant velocity linear self-motion - the aim being to maximize vection by minimizing visual-vestibular conflict. However, it has been found that adding horizontal or vertical perspective jitter/oscillation (similar to the effects of camera shake) to these radial flow patterns enhances vection induced in stationary subjects (Palmisano et al., 2000, 2003; 2007). This vection advantage cannot be explained by traditional conflict theories. In order to better understand the role that visual-vestibular sensory integration plays in self-motion perception we examined an active head movement scenario. Method. The computer generated visual self-motion stimulus consisted of 1536 random dots placed uniformly within a 3D spatial environment. Constant-velocity forward self-motion was simulated by moving the dots toward the camera viewpoint at a rate of 0.75 of the total depth between the near and far clipping planes for each second in time elapsed. A 120fps digital camera was used to acquire images of a small infrared headset fitted to the top of the participants head. The images pixels were analysed in real-time using custom software written in C++ to obtain linearised inter-aural head position in centimetres. Head position data were then transmitted to the 3D rendering application to update the camera position in-line with the participants changing head position (active jitter condition). Head position data were recorded to file and could be used without head tracking to reproduce active visual jitter during a subsequent condition where the head was stationary (passive jitter condition). Participants swayed side to side at the waist along the inter-aural axis to a metronome triggering an audible cue every 0.5 second. During these 1.0Hz lateral head oscillations, randomised 30-second trials were used to display either non-jittering optic flow or laterally oscillating optic flow synchronized with inter-aural head position. Ratings of the perceived strength of induced vection were obtained from seven participants. Results. Vection strength ratings obtained with active head oscillation and synchronized display jitter were significantly greater than those without display jitter. The vection ratings produced by passively viewing display jitter were also significantly great than the non-jittering controls, as reported by Palmisano et al. previously. Conclusion. These findings show that visual display jitter enhances vection in depth, both when passively viewed or when viewed under active control. The similarity in vection ratings between active and passive conditions suggests that the addition of synchronized input from the otoliths consistent with the pattern of optic-flow jitter did not enhance vection more than that reported with passively viewed jittering flow.

Publication Date


  • 2008

Citation


  • Kim, J. & Palmisano, S. A. (2008). Global perspective jitter enhances vection in both active and passive observers. XXV Barany Society Meeting Program and Abstracts (pp. 347-347). Kyoto, Japan: Barany Society.

Start Page


  • 347

End Page


  • 347

Place Of Publication


  • Kyoto, Japan