Theoretical considerations on models of vestibular self-motion perception as inherent in computational frameworks of motion sickness

Abstract

This study examines self-motion perception incorporated into motion sickness models. Research on modeling self-motion perception and motion sickness has advanced independently, though both are thought to share neural mechanisms, making the construction of a unified model opportune. Models based on the Subjective Vertical Conflict (SVC) theory, a refinement of the neural mismatch theory, have primarily focused on motion sickness, with limited validation for self-motion perception. Emerging studies have begun evaluating the perceptual validity of these models, suggesting that some models can reproduce perception in specific paradigms, while they often struggle to jointly capture motion perception and sickness. One prior study demonstrated that one of the SVC models could replicate illusory tilt during centrifugation, while others produced unrealistic responses, such as persistent tilt after motion cessation. In reality, under steady-state conditions such as being motionless, perceived motion is expected to settle to an appropriate state regardless of prior states. Based on the idea that this behavior is closely related to the equilibrium points and stability of the model dynamics, this study theoretically analyzed 6DoF-SVC models with a focus on them. Results confirmed that only one model ensures convergence from any state to a unique equilibrium point corresponding to plausible perception. In contrast, other SVC models and a conventional self-motion perception model converged to values dependent on earlier states. Further analysis showed that only this model captured both the somatogravic and Ferris wheel illusion. In conclusion, this 6DoF-SVC model unifies motion perception and sickness modeling, with theoretical convergence of the perceptual state.

Keywords: Computational model; Motion sickness; Subjective vertical conflict theory; Vestibular self-motion perception.

Fig. 1

Overview of the 6DoF-SVC (In1) model (Inoue et al. 2023). There are several possible forms of the model, which differ in terms of the existence and absence of integrals the feedback process depicted in part X. For example, the original 6DoF-SVC model (Kamiji et al. 2007) (later (In3) model) includes integrals for all three feedback signals

Fig. 2

Simulation results for the Ferris wheel illusion with (a) the 6DoF-SVC (In1) model and (b) the Merfeld model. The upper two signals represent inputs of the models: GIA f and angular velocity . The lower three signals are the model simulated perceived motion: , , and

Fig. 3

Simulation results for the somatogravic effect with (A) the fixed-radius condition and (B) the variable-radius conditions. For each condition, the left and right figures illustrate the results using (1) the 6DoF-SVC (In1) model and (2) the Merfeld model. For each graph, the upper two signals represent inputs of the models: GIA f and angular velocity . The lower two signals are the model simulated perceived motion: and perceived head tilt calculated from . The perceived tilt plots also include the average response obtained from multiple participants, digitized from Merfeld et al. (2001) for direct comparison. Similarly, the slow-phase velocity of the horizontal VOR obtained from Merfeld et al. (2001), inverted in sign, is overlaid with the plots of  for the fixed-radius condition. For the variable-radius condition, however, the result was not overlaid because the experimental data provided in that paper correspond only to the steady-state phase (at 200 s in the figure), and they show values close to zero, which is consistent with the simulated results