Multisensory processing during self-motion

想想你或你的朋友感到晕车的时候。也许你在弯弯曲曲的路上坐在汽车的后座上。也许，你在玩游乐设施，你和你的朋友坐在一艘宇宙飞船上，在虚拟世界里飞驰。为什么你们只有一个人生病了？现在想象一次你摔倒了。也许你绊倒了，从楼梯上摔了下来，或者在冰面上滑倒了。你能很好地回忆起从坠落开始发生的全部事件吗？也许你只记得一个瞬间，比如天空的蔚蓝，或者在你下楼的时候伸手去抓栏杆。相对而言，我们对自我运动时的感觉信息是如何处理的（在跌倒时就更不了解了）以及如何预测个人晕车的发病率知之甚少。我过去的研究表明，大脑在处理前庭信号（关于头部运动的信息）以产生反射反应和做出感知反应的过程中是分离的，并且在判断感知到的感官事件的相对时间时，个体是不同的。本提案的目标是建立一个综合模型，说明多感官事件的时间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)自我运动过程中多感官事件的感知时间。我最近的研究发现，前庭信息必须先于其他感官事件出现，才能被视为同时发生。这表明，令人惊讶的是，前庭感知是缓慢的，而前庭反射是快速的。我希望在人们跌倒时也能找到类似的结果。前庭延迟知觉的参数化评估与自我运动的生理和神经反应相结合，将用于构建前庭延迟知觉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官线索。为了定量地研究自我运动的线索组合，独立测量了与视觉和前庭对自我运动的估计相关的方差，通过最大似然积分器组合，并将其与存在两种线索的感知自我运动进行比较。我认为，文献中发现视觉和前庭线索最佳整合的差异是由于自我运动期间视觉敏感性的变化和感觉线索之间的感知时间延迟造成的。(3)自我运动时晕车的对策。感觉冲突发生在人造环境中，经常导致晕动病，其严重程度和发病率因人而异。众所周知，运动模拟器中的时间延迟会引起晕动病，工程师们尽最大努力将视觉和前庭信号之间的时间延迟减少到零。我希望，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，晕动病可以最小化。我的研究项目认识到前庭系统是认知的基础。了解前庭信息是如何临时处理的，以及它是如何影响感知到的自我运动的，这不仅对了解大脑如何工作至关重要，而且对减少晕动病的发病率也至关重要，晕动病阻碍了在航空、航天、设计、移动计算和医疗保健行业更广泛地采用节省成本的虚拟现实技术。同样，更深入地了解前庭信息加工与反射反应之间的分离，可以帮助开发预防性干预措施，以帮助减少跌倒相关伤害；给加拿大经济造成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).