PROCESSING STREAMS IN EARLY VISION

视觉能让我们活在未来，在事情发生之前看到它们并做出反应。视觉对生物体的优势是压倒性的，在视觉的所有预测功能中，对运动的感知可以说是最有价值的：它明确而迅速地处理事物的位置，而不仅仅是事物的方向。事实上，运动感知的优势是如此之大，以至于在人类视觉系统中出现了两种截然不同的运动系统。这项拨款的目标是定义和描述这两个系统中最不为人所知的，即“高级”运动系统。我们的工作表明，高级系统似乎是基于注意力对目标的选择和追求，这个系统在许多方面类似于眼球运动的平滑追求系统。细心的跟踪是许多日常活动的关键部分——驾驶、运动和对动态计算机显示的反应。了解它的局限性和机制，而不是低级运动检测器的特性，对于理解人类在苛刻环境中的表现至关重要。我建议在正常人和顶叶区域受损的个体中研究注意力在高级视觉中的作用，顶叶区域是一个涉及注意力的区域。为了分离高级运动系统，我们还必须了解基于视觉皮层中定向选择神经元的低级运动系统。计划进行几个实验，以确定低级过程并对其数量和性质进行分类。我们还将继续研究用眼球运动跟踪目标时使用的平滑追踪系统。我们的早期结果表明，高水平的运动信号可能在启动和纠正平滑追求中发挥重要作用。最后，我们看看视觉系统如何识别刺激的位置，尽管不断大大小小的眼睛运动。我们发现了一种稳定系统，一种“稳定凸轮”过程，基于低水平的运动信号，尽管眼睛在运动和振动，但它能保持世界的稳定。我们将继续我们在这些项目上的工作，并开始一个关于从视野外感知刺激的新项目。在最后一项研究中，我们将通过巩膜刺激视网膜，并解决如何根据凝视方向纠正物体的感知位置的问题。我们将研究对刺激的早期反应是否被限制在对凝视方向的意识之外，其中受刺激的视网膜位置对应于正常视野之外的位置。在这些最后的研究中，我将测试正常和神经受试者，并使用功能磁共振成像记录大脑活动。

Vision allows us to live a little bit in the future, to see things and react to them before they actually bump into us. The advantages of vision to an organism are overwhelming and, of all of the predictive functions of vision, the perception of motion is arguably the most valuable: it explicitly and rapidly deals with not just where things are but where things are going. In fact, the advantages of motion perception are so great that two very different motion systems appear to have emerged independently in the human visual system. The goal of this grant is to define and characterize the least understood of these two systems, the "high-level" motion system. Our work has shown that the high-level system appears to be based on selection and pursuit of targets by attention, a system analogous in many ways to the smooth pursuit system of eye movements. Attentive tracking is a critical part of many everyday activities - driving, playing sports, and responding to dynamic computer displays. Understanding its limitations and mechanisms in isolation from the properties of low-level motion detectors is crucial to understanding human performance in demanding environments. I propose to study the role of attention in high-level vision in normals and in individuals with damage to the parietal region, an area involved in attention. To isolate the high-level motion system, we must also understand the low-level system which is based on directionally selective neurons in the visual cortex. Several experiments are planned to identify low-level processes and catalog their number and properties. We also will continue to examine the smooth pursuit system used when tracking targets with eye movements. Our early results show that high-level motion signals may play a significant role in initiating and correcting smooth pursuit. Finally, we look at how the visual system identifies the position of stimuli despite constant large and small motions of the eye. We have discovered a stabilization system, a "Steadycam" process, based on low-level motion signals that keeps the world stable despite movement and vibration of the eye. We will continue our work on these projects and begin a new project on the perception of stimuli from outside the visual field. In this last study we will stimulate the retina through the sclera and address the question of how the perceived location of object is corrected for the direction of gaze. We will examine whether the early responses to the stimulation are gated out of awareness for directions of gaze where the stimulated retinal location corresponds to a location outside the normal visual field. In these final studies I will test normal and neurological subjects and record brain activation using fMRI.