Development of Visual Stability in Human Infants

这项研究项目的目标是确定幼儿在什么年龄以及通过什么潜在的机制认为视觉世界是稳定的，尽管眼睛、头部和身体都在移动。成年人认为视觉世界是稳定的，尽管主要是通过视觉和前庭刺激引发的反射性眼球运动来进行自我产生的运动。这些眼球运动有助于减少或消除由自身产生的运动所产生的视网膜图像的运动。前庭-眼反射(VOR)由头部的旋转或平移触发，使眼睛在与头部运动相反的方向上反转。视动反射(OKR)将眼睛朝视网膜图像移动的方向移动。这些反射由位于当前凝视方向附近的视网膜图像速度的细粒度分析补充，并转换为平滑追踪系统的眼动信号。在典型的视觉环境中，物体在许多不同的距离，观察者必须选择一个深度平面来注视，并抑制由距离较近和较远的物体产生的视网膜图像运动。当视觉场景移动时，无论是由于物体的移动还是观察者的移动，三个眼动系统--VOR、OKR和平滑追踪--被协同激活以稳定被关注的对象，而不管其他视网膜图像的移动。这些实验将让2到6个月大的人类婴儿在头部/身体保持稳定位置时显示移动的视觉显示，或者在头部/身体横向移动时显示固定的视觉显示。前一条件刺激OKR和平滑追踪系统，后一条件刺激这三个系统以揭示VOR的作用。争论的焦点是，尽管视觉环境和/或头部/身体的运动，婴儿如何能够有效地将注意力对象稳定在视网膜上。根据早期的研究表明，平滑追逐直到2个月龄才会出现，深度知觉直到4个月龄才会出现，Aslin预测，如果平滑追逐系统是关键因素，那么2个月龄应该会出现有效的稳定。然而，如果物体的深度分离是关键因素，那么直到4个月龄时才会出现有效的稳定。这些来自正常婴儿的结果将为理解三个眼球运动系统的发展提供基线，这三个眼球运动系统对于成年人感知稳定的视觉世界至关重要。

The goal of this research project is to determine at what age and with what underlying mechanism young infants perceive the visual world as stable despite movements of the eyes, head, and body. Adults perceive the visual world as stable despite self-produced movements primarily by means of reflexive eye movements triggered by visual and vestibular stimulation. These eye movements serve to reduce or eliminate those movements of the retinal image that are created by self-produced movements. The vestibulo-ocular reflex (VOR), triggered by rotations or translations of the head, counter-rolls the eyes in the direction opposite to head movement. The optokinetic reflex (OKR) moves the eyes in the direction of retinal image movement. These reflexes are supplemented by a fine-grained analysis of retinal image velocities located near the current direction of gaze and converted into eye movement signals for the smooth pursuit system. In a typical visual environment with objects at many different distances, the observer must select a depth-plane for fixation and suppress those retinal image motions created by objects at nearer and farther distances. When the visual scene moves, either because of object movement or movement of the observer, the three oculomotor systems -- VOR, OKR, and smooth pursuit -- are activated in concert to stabilize the attended object despite the movements of other retinal images. These experiments will present 2- to 6-month-old human infants either with moving visual displays while they are held in a stable head/body position or with stationary visual displays while their head/body is moved laterally. The former condition stimulates the OKR and smooth pursuit systems, while the latter condition stimulates all three systems to reveal the role of the VOR. At issue is how effectively infants are able to keep the object of attention stabilized on the retina despite movements of the visual surround and/or movements of the head/body. Based on earlier work showing that smooth pursuit does not emerge until 2 months of age and depth perception does not emerge until 4 months of age, Aslin predicts that if the smooth pursuit system is the critical factor, then effective stabilization should emerge at 2 months of age. However, if segregation of objects in depth is the critical factor, then effective stabilization should not emerge until 4 months of age. These results from normal infants will provide a baseline for understanding the development of three oculomotor systems that are known to be essential for adults' perception of a stable visual world.