Carver Sean, Kiemel Tim, Jeka John J
Department of Kinesiology, University of Maryland, College Park, MD, USA.
Biol Cybern. 2006 Aug;95(2):123-34. doi: 10.1007/s00422-006-0069-5. Epub 2006 Apr 26.
Reweighting sensory information adaptively is considered critical for flexible postural control, but little is known of the time scale of the reweighting process. We analyzed the transient dynamics of sensory reweighting in a previously published nonlinear adaptive model of sensory integration in the human postural control system. The model's dynamics of adaptation were tested in response to abrupt changes in the amplitude of the motion of the visual surround. In addition to qualitatively reproducing the correct asymptotic response to such changes in visual amplitude, as previously found, the model qualitatively reproduced the asymmetric transient response elucidated in recent experiments (Oie et al. in Gait Posture 2005). In particular, the model adapts at an initially rapid rate to a switch from low to high amplitude visual motion, but at an initially slower rate upon the return to low amplitude motion. The observed temporal asymmetry has potential functional value. Rapid downweighting of a visual stimulus that suddenly increases is necessary to prevent loss of upright equilibrium. A visual stimulus that decreases in amplitude does not pose a threat to upright balance, allowing for slower upweighting without functional consequence.
自适应地重新加权感觉信息被认为是灵活姿势控制的关键，但对于重新加权过程的时间尺度却知之甚少。我们在先前发表的人体姿势控制系统感觉整合的非线性自适应模型中分析了感觉重新加权的瞬态动力学。该模型的适应动力学是针对视觉环境运动幅度的突然变化进行测试的。除了定性地再现对视觉幅度这种变化的正确渐近响应（如先前发现的那样）之外，该模型还定性地再现了最近实验中阐明的不对称瞬态响应（Oie等人，《步态与姿势》，2005年）。特别是，该模型在从低幅度视觉运动切换到高幅度视觉运动时最初以快速速率适应，但在返回低幅度运动时最初以较慢速率适应。观察到的时间不对称具有潜在的功能价值。突然增加的视觉刺激的快速减权对于防止失去直立平衡是必要的。幅度减小的视觉刺激不会对直立平衡构成威胁，允许较慢的加权增加而没有功能后果。
