| dc.description.abstract | After centuries, still no consensus regarding the exact mechanisms behind motion sickness has been achieved. However, it seems to be related to the amount of postural sway, either via a causal effect, the “Postural Instability Theory” (PIT), or because they are both influenced by a common factor, the “Subjective Vertical Theory” (SVT). Besides distraction, no cognitive aspects of motion sickness had been examined yet, despite proof of it having an effect on self-motion perception. Cognitive manipulation of the self-motion expectation was tested using a custom built parallel swing, as participants were exposed to an oscillatory lateral movement while imagining the direction of their self-motion either correctly or incorrectly. COP data were gathered before and after exposure. Differences in postural sway, defined as RMS amplitudes in AP/ML direction and length of COP path, were calculated. A significant increase in postural instability after exposure was found for all measures. No significant effect of imagination on the amount of postural instability was found. Furthermore, no differences in sway increase between non-sick and sick participants were found, arguing the PIT being false. The absence of the imagination effect could indicate that imagination of self-motion is not powerful enough to influence the subjective vertical. This could be due to the motion not being ambiguous enough to be misinterpreted, as the majority of participants reported not being misled by the incorrect imagination. Thus, further research should increase ambiguity of the motion to properly address the effects of self-motion expectation on motion sickness and postural instability | |
