Multisensory processing during self-motion

想一想你或你的朋友感到晕车的一次。也许你坐在一辆汽车的后座上，在一条曲折的道路上。也许，你正坐在游乐设施上，你和你的朋友在一艘宇宙飞船上绕着虚拟世界飞驰。为什么你们中只有一个人生病了？现在想象一下你摔倒的时候。也许你被绊倒了，从楼梯上摔了下来，或者在冰上滑倒了。你能很好地回忆起从秋天开始的整个事件序列吗？也许你只记得那一刻，比如天空的蔚蓝，或者在你下山的路上伸手到栏杆上。我们对自我运动过程中感觉信息是如何处理的知之甚少(跌倒时就更少了)，也知道什么可以预测个人晕动病的发生率。我过去的研究表明，大脑分离了它处理前庭信号(关于头部运动的信息)以产生反射反应和做出知觉反应的方式，而且在判断感知到的感觉事件的相对时机时，每个人都有所不同。这项建议的目标是开发一个全面的模型，说明多感觉事件的时序如何影响对自我运动的感知、生理和神经反应。我将发展三个主题：(1)自我运动中多感官事件的感知时序。我最近的工作发现，前庭信息必须在其他感觉事件之前呈现，才能被感知为同时发生。这表明，令人惊讶的是，前庭感觉很慢，而前庭反应很快。我希望在人们摔倒时也能得到类似的结果。我们将使用对感知前庭延迟的迫切需要的参数评估，以及对自我运动的生理和神经反应来构建前庭延迟感知的神经机制的理论模型。(2)自我运动过程中的感觉线索整合。最大似然估计可以用来可靠地预测大脑如何整合感觉线索。为了定量研究自我运动的线索组合，通过最大似然积分器独立测量与自我运动的视觉和前庭估计相关的方差，并将其与存在这两个线索的感知的自我运动进行比较。我认为，文献中在寻找视觉和前庭线索最佳整合方面的差异是由于自我运动过程中视觉敏感度的变化以及感觉线索之间的时间延迟。(3)自主运动中的晕动病对策。感觉冲突发生在人为环境中，通常会导致晕动病，其严重程度和发病率因个体而异。众所周知，运动模拟器中的时间延迟会导致晕动病，工程师们尽最大努力将视觉和前庭提示之间的时间延迟减少到零。我预计，当这种时间延迟相对于每个人的主观同时性点进行校准时，晕动病可以最大限度地减少。我的研究计划承认前庭系统的作用是认知的基础。了解前庭信息是如何在时间上处理的，以及它如何影响感知的自我运动，不仅对于了解大脑是如何工作的，而且对于减少晕动病的发生率至关重要。晕动病阻碍了节省成本的虚拟现实技术在航空、空间、设计、移动计算和医疗保健行业的广泛采用。同样，更深入地了解处理前庭信息以进行反射反应与有意识意识之间的分离，可以帮助开发预防性干预措施，帮助减少与跌倒相关的伤害；加拿大经济将面临30亿美元的负担(加拿大公共卫生局)。

Think about a time you or a friend felt motion sick. Perhaps you were in the backseat of a car on a twisty road. Maybe, you were on an amusement ride, where you and your friend were on a spaceship zipping around a virtual world. Why is it that only one of you got sick? Now imagine a time you fell down. Perhaps you tripped, fell down the stairs, or slid on some ice. Do you have a good sense of recalling the full sequence of events from the onset of the fall? Perhaps you remember just one moment such as the blueness of the sky or reaching out to a rail on your way down. We know relatively little about how sensory information is processed during self-motion (even less during a fall) and what can predict the incidence of motion sickness across individuals. My past research has shown that the brain dissociates how it processes vestibular signals (information about head movement) for generating reflexive responses and for making perceptual responses, and that individuals vary when judging the perceived relative timing of sensory events. The goal of this proposal is to develop a comprehensive model of how the timing of multisensory events affects perceptual, physiological, and neural responses to self-motion. I will develop three themes: (1) PERCEIVED TIMING OF MULTISENSORY EVENTS DURING SELF-MOTION. My recent work has found that vestibular information must be presented prior to other sensory events in order to be perceived as simultaneous. This suggests, surprisingly, that vestibular perception is slow while vestibular reflexes are fast. I expect to find similar results when people fall. Much needed parametric assessment of perceived vestibular delay paired with physiological and neural responses to self-motion will be used to construct a theoretical model of the neural mechanisms that subserve delayed vestibular perception. (2) SENSORY CUE INTEGRATION DURING SELF-MOTION. Maximum-likelihood estimation can be used to reliably predict how sensory cues are integrated by the brain. To investigate cue combination for self-motion quantitatively, variances associated with visual and vestibular estimation of self-motion are independently measured, combined by a maximum-likelihood integrator, and compared to perceived self-motion with both cues present. I expect that discrepancies in finding optimal integration of visual and vestibular cues in the literature result from change in visual sensitivity during self-motion and perceived temporal delays between sensory cues. (3) MOTION SICKNESS COUNTERMEASURES DURING SELF-MOTION. Sensory conflict occurs in man-made environments, often leading to motion sickness whose severity and incidence varies widely across individuals. Temporal delay in motion simulators is well known to induce motion sickness and engineers do their best to reduce temporal delay between visual and vestibular cues to zero. I expect that motion sickness can be minimized when this temporal delay is calibrated relative to each individual’s point of subjective simultaneity. My research program recognizes the role of the vestibular system as fundamental to cognition. Knowing how vestibular information is temporally processed and how it affects perceived self-motion is critical not only to understand how the brain works but also to reduce the incidence of motion sickness, which is holding back wider adoption of cost-saving virtual reality technology in the aviation, space, design, mobile computing, and healthcare industries. Likewise, a deeper understanding of the dissociation between processing vestibular information for reflexive responses versus conscious awareness could help in the development of preventative interventions to help reduce fall-related injury; a $3 billion burden to the Canadian economy (Public Health Agency of Canada).