隨著相關技術和配套基礎設施的成熟，虛擬實境（VR）已逐漸被應用到各種不同的領域，然而，缺乏沉浸感和因虛擬實境而造成之相關動暈症仍然被認為是阻礙公眾接受實境普及的關鍵因素。
由於目前只有少數的研究有特別針對相關因子間的交互作用，且只有少量的評估動暈症的方法，本研究將解決這兩個問題，透過延伸現有利用姿勢不穩評估動暈症的方法探討行走穩定性，此外本研究透過主觀評量、步態分析與皮質變化量量測探討了導航控制和可見視域（FOV）對使用者於虛擬實境中所感受的存在感和可能觸發之動暈症的影響，最後，本研究欲找出減少凍暈症並同時維持沈浸感之意涵且利用步態模式和皮質活動找出步態穩定性與動暈症之關係。
共有30名（男15名，女15名）年齡在20 ~ 35歲之間的健康受試者參與本研究實驗，他們透過使用頭載式顯示裝置，於虛擬環境下進行一系列的障礙躲避射擊任務，在執行VR任務時，每一天都會分別於虛擬環境內，使用全視野和限制視野兩種不同的視場模式進行，而在三天的實驗過程中，則是在任一天選擇使用Xbox控制導航、頭部導航、和自然運動導航，共三種不同的導航控制方法進行任務。
在每次12分鐘的障礙躲避射擊任務進行前後，受試者需要透過SSQ、FMS和PQ問卷對暴露於快節奏動作的視覺刺激虛擬環境進行對使用體驗的主觀評量，本研究分析暴露於虛擬實境前與後之行走任務下的步態模式與皮質活動，探討動暈症對於行走穩定性的影響與維持穩定行走的相關神經區。
研究結果顯示，與頭部和自然導航模式相比，Xbox導航造成之暈屏程度更高，且存在感水準也較低，此外，相對於頭部導航，受試者於使用自然運動導航控制時，其於虛擬實境內所感受到之存在度，明顯較高，而在視域範圍的影響方面，當使用Xbox導航控制中，相較於全視場模式，於虛擬環境內使用限制視場的顯示模式，受試者更容易產生暈屏的現象，然而，這個現象在使用其他兩種導航模式時，並沒有被觀察到。
最後，在任務表現上，自然導航模式的表現最佳，頭部導航次之，Xbox導航的表現則最差，在步態方面，正常走路下的時間步態參數，相對於空間步態參數，是更好的動暈症指標，相較於暴露於虛擬環境前，暴露於虛擬環境後的倒退慢速走路（Backwards Tandem Gait）的步態變異較大，而在關節部位的角度變化上，暴露於虛擬環境後的髖、膝蓋、腳踝關節角度變化都與跌倒年長者的關節部位角度變化相似，此外在前額葉含氧血濃度變化方面，在暴露於虛擬實境前與後的行走任務時的前額葉含氧血濃度變化有顯著的差異。
整體看來，為了在不造成明顯不適之暈屏症狀下，獲得理想之沉浸式體驗，未來使用VR於教育訓練、現場作業，或復健相關之應用場域時，虛擬實境內容提供者應該根據虛擬環境（VE）中特定的視覺內容和需要執行的任務模式，仔細設計其導航控制和選擇適當之視場顯示範圍。

With the advent of technology and supporting infrastructure today, diverse applications of VR continue to develop and expand. However, lack of immersion and prevalence of cybersickness due to virtual environment (VE) exposure are still problems that hinder the acceptance of VE among the general public. With limited investigation on the interactions between factors that induces cybersickness and limited evaluation methods for cybersickness, this study seeks to tackle both problems. By extending the current evaluation method of postural instability to encompassing gait stability, this study examined the effects of navigational control and field-of-view (FOV) on cybersickness and presence levels using subjective measurements, gait analysis and cortical measurements. The aim is to discover possible valuable insights into reducing cybersickness while maintaining the overall immersion experience as well as explore the relationship of gait stability and cybersickness through gait patterns and cortical activations.
Thirty healthy participants (15 male and 15 females) within the age range of 20-35 years old played an obstacle-avoidance shooting game under the exposure of the VE and performed sets of gait tests pre and post exposure to the VE. The VR game was performed using combinations of three different navigational control method: Xbox gamepad navigation, Head-based navigation, and Natural locomotion navigation, along with two FOV modes of the visual scenes: Full-FOV and Restricted-FOV on three separate days. Subjective ratings of cybersickness and presence levels were collected and evaluated using SSQ, FMS, and PQ. Gait patterns and cortical activity during the gait tests before and after the exposure of the VE were analyzed to examine the influence of cybersickness on gait stability as well as the neural correlates necessary for maintaining stable walking.
The results for this study showed that greater cybersickness level and lesser presence level was associated with the Xbox navigation than the Head and Natural navigations. Moreover, Natural navigation led to greater presence level relative to Head and Xbox navigations. As for the effect of FOV modes, the Restricted-FOV mode was found to induce lesser cybersickness than those of Full-FOV mode in the Xbox navigation, whereas no difference was observed in the other two navigation conditions. As for the task performance, Natural navigation had the best performance, followed by Head navigation, with Xbox navigation having the worst performance. In terms of gait patterns, normal gait showed temporal parameters being more sensitive to cybersickness than spatial parameters and gait variabilities. Backwards tandem gait showed greater gait variabilities in the post-exposure stages compared to those of pre-exposure stages. Gait kinematics of hip, knee and ankle joints in the post-exposures demonstrated similar gait patterns to those of elderly fallers. In terms of cortical activations, prefrontal cortex activations during locomotion showed differences in activation levels between the stages. Altogether, to achieve the desired immersion experience without inducing detrimental cybersickness, the future application of VR in training or rehabilitation should carefully design the navigational control and the FOV range with respect to the specific visual contents and task modalities performed in the VE.

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