宇航员进入太空之后会产生空间运动病，持续2~4天后症状可自动消失，而当宇航员从长期航天飞行环境回到地面后会发生前庭功能暂时紊乱，需要一段时间来重新适应地面生活所需要的平衡和空间定向能力。显然在这一过程中，来自前庭系统对重力变化的适应引发了其他系统（如视觉、体感等）产生相应的适应来抵消不同感觉之间冲突造成的不适。但是不同感觉之间适应是如何相互影响的神经机制尚不清楚。本项目通过在非人灵长类身上对前庭-视觉错觉适应的神经机制进行探索，将基于贝叶思理论的最优知觉行为整合理论和基于强化学习理论的奖励决策制定/行为选择结合起来，探索视觉、前庭觉及其相互作用影响认知加工的动态变化规律。这些研究将有助于对空间运动病及空间定向障碍中枢整合机制的了解，为探索新的航天员前庭功能训练方法提供理论依据。

Astronauts experience similar sensations of dizziness and disorientation during their first few days in the microgravity environment of space. Upon returning to Earth after prolonged exposure to microgravity, astronauts frequently have difficulty standing and walking upright, stabilizing their gaze, and walking or turning corners in a coordinated manner. An astronaut's sense of balance and body orientation takes time to re-adapt to Earth-normal conditions. While studies have identified the source of these changes to occur at the level of the central nervous system, the basic mechanisms underlying multisensory perceptual adaptation are currently unclear. To what extent does multisensory adaptation follow Bayesian-like (cue-reliability dependent) calibration? How does motivation/reward (reinforcement learning) influence multisensory adaptation? What is the neuronal substrate for multisensory adaptation? In this study I shall address these questions through psychophysics experiments and electrophysiological recording in non-human primates. The subject’s task will be to discriminate heading direction experienced during either single-cue or combined presentation of vestibular and visual (optic flow) input. During the trials, multisensory adaptation will be induced by introducing a discrepancy between the two (visual/vestibular) cues, and studied in the presence and absence of reinforcement. I hypothesize that dynamic adaptation of multisensory integration is driven by a combination of Bayesian theory and reinforcement learning, and intend to model it accordingly. Furthermore, I expect to find the neural correlate of Bayesian vs. reinforcement based adaptation in the cerebellum and basal ganglia, respectively. The dorsal medial superior temporal (MSTd) cortex, which has recently been associated with visual-vestibular integration, most likely integrates sub-cortical Bayesian and reinforcement-based adaptation, thereby manipulating the subject’s heading perception. The results of the proposed research will guide future investigations of sensorimotor changes in astronauts and assist their adaptation to life on earth.