PROCESSING STREAMS IN EARLY VISION

视觉让我们能够活在未来，在它们真正撞到我们之前看到它们并对它们做出反应。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：它不仅明确和快速地处理事物的位置，而且还处理事物的去向。事实上，运动感知的优势是如此之大，以至于人类视觉系统中似乎出现了两种截然不同的运动系统。这笔赠款的目的是定义和描述这两个系统中最不为人所知的“高级”动议系统。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逐，这一系统在许多方面类似于眼球运动的平滑追逐系统。注意力跟踪是许多日常活动的关键部分--开车、运动和对动态计算机显示做出反应。从低水平运动探测器的特性出发，了解其局限性和机制，对于理解人类在苛刻环境中的表现至关重要。我建议研究注意力在高水平视觉中的作用，在正常人和顶区受损的人中，顶区是一个涉及注意力的区域。为了分离高级运动系统，我们还必须了解低级别系统，该系统基于视觉皮质中的方向选择性神经元。计划进行几项实验，以确定低级别流程并对其数量和属性进行分类。我们还将继续研究跟踪眼动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稳追踪中起着重要作用。最后，我们看看视觉系统如何识别刺激的位置，尽管眼睛不断地做着大小的运动。我们已经发现了一种稳定系统，一种基于低水平运动信号的“稳定摄像头”过程，它可以在眼睛运动和振动的情况下保持世界的稳定。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之外感知刺激的新项目。在这最后一项研究中，我们将通过巩膜刺激视网膜，并解决如何校正物体的感知位置以适应凝视方向的问题。我们将检查对刺激的早期反应是否出于对凝视方向的感知，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，我将测试正常的和神经学的受试者，并使用功能磁共振成像记录大脑的激活。

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.