Izadi Sokhtabandani, Siyavash2026-06-152026-06-152026-06-152026-06-12https://hdl.handle.net/10012/23608This dissertation investigates how the brain dynamically reweights sensory cues to resolve multisensory conflicts in virtual reality (VR), with a specific focus on the etiology of cybersickness. The research characterises how visual, vestibular, and proprioceptive cues are integrated and recalibrated following VR gameplay while accounting for individual differences in these processes which dictate susceptibility to sickness. Across three experiments, this work challenges the assumption that VR exposure triggers a uniform sensory shift. Experiment 1 utilised the Subjective Visual Vertical (SVV) task, finding that high-intensity exposure shifted participants' perceived upright toward gravitational vertical and away from the body axis. Crucially, individuals who demonstrated greater reweighting reported lower cybersickness, suggesting that rapid sensory adaptation acts as a protective mechanism. Experiment 2 employed the Oriented CHAracter Recognition Test (OCHART) to further tease apart the relative weighting of visual and gravitational cues. While VR exposure did not produce a uniform group-level shift in the Perceptual Upright (PU), exploratory analyses revealed that increased visual weighting post-exposure was associated with higher cybersickness, indicating that a failure to down-weight unreliable visual inputs may be maladaptive. Experiment 3 attempted to manipulate these weights by degrading vestibular reliability through stochastic electrical vestibular stimulation (EVS). Contrary to the hypothesis that reducing vestibular certainty would force a beneficial reweighting, EVS exacerbated cybersickness and increased attrition, while cue-weighting models remained unstable. Altogether, this work demonstrates that cybersickness is not merely a product of sensory conflict, but a failure of the central nervous system to successfully reweight unreliable cues. The results suggest a two-part interpretation: first, that individual differences in sensory plasticity may relate to tolerance, where greater post-VR shifts toward gravitational cues were associated with lower symptom severity in Experiment 1, though this relationship was not consistent across tasks and measures. Second, the results suggest that external disruption of vestibular signals (via EVS) may hinder rather than help adaptation. These findings provide preliminary evidence for a reweighting account of individual differences in cybersickness susceptibility and point toward personalised exposure protocols as a candidate intervention, pending replication with larger and more diverse samples.enmultisensory integrationcybersicknesssensory reweightingDoctoral Thesis