Spatiotemporal representation in ventral visual pathway

在自然视觉中，对象在平移、旋转、被遮挡或经历时会随着时间的推移而改变外观 复杂的变化，例如，在生物运动期间。在这些动态的环境中，视觉皮质 集成多个空间和时间尺度上的信息以计算运动轨迹并表示 物体的形状。为了理解形状和运动感知是如何从这种动态视觉中派生出来的 输入，我们将研究V4区的神经元反应-腹侧视觉的中间阶段 路径-由时变的视觉刺激的时空整合形成。我们将测试 假设V4神经元的时空特性适合跟踪动态对象： 具体地说，V4运动信号产生于比可比的更长的时空窗口上的对象跟踪 以及V4信号在对象级别而不是在级别上反映形式变换 当地的视网膜图像。我们将利用远程视在运动的感知来探索V4的作用 运动知觉中的神经元(目标1)。当刺激间歇性地跳过视场时 空间和时间步骤，它诱导了强烈的虚幻运动知觉，但背侧V1和MT的神经元 视觉流对感知到的运动的方向非常不敏感。心理物理学研究已经 认为远距离的表观运动不依赖于背部流，而是依赖于更高阶的物体跟踪 腹侧视流中具有较大时空窗口的过程。我们将进行第一次 对清醒猴进行神经生理学研究，以确定V4在长时间刺激知觉中的作用 视在运动范围。接下来(目标2)，我们将使用在正面平行平面上旋转的动态刺激，以及 深度平移和旋转，以确定V4神经元是否编码其他常见的动态对象 转换(远距离转换之外)，以及编码是否基于静态序列 姿势，如在下颞叶(IT)皮质，或动态转换。最后，我们将检查编码 以及对部分遮挡的动态对象的感知(目标3)。当被遮挡的对象移动时，不同的部分 随着时间的推移和跨时间的整合以及多个神经元感受野被揭示 生成整个对象表示所需的。当动物辨别移动的被遮挡的物体时，我们将 用高密度神经素探针研究50-100个神经元。我们将使用单次试验总体解码 确定如何跨V4网络集成动态刺激信息以提取对象的方法 形状和运动轨迹，以及V4如何影响心理物理行为。我们预计我们的 结果将揭示V4在动态刺激处理中的重要作用，它是对这些刺激的补充 并将建立在V4中运行的内部视觉表征的水平。我们的研究将 提供对全局运动感知和动态跟踪的神经元基础的更深入的理解 对象-在老龄化人群中受损的过程，特别是那些患有阿尔茨海默病的人。

In natural vision, objects change appearance over time as they translate, rotate, become occluded or undergo complex transformations, e.g., during biological motion. In these dynamic environments, the visual cortex integrates information over multiple spatial and temporal scales to compute motion trajectories and represent the shape of objects. To understand how form and motion percepts are derived from such dynamic visual input, we will investigate how neuronal responses in area V4—an intermediate stage along the ventral visual pathway—are shaped by the spatiotemporal integration of time-varying visual stimuli. We will test the hypothesis that the spatiotemporal characteristics of V4 neurons are suited for tracking dynamic objects: specifically, V4 motion signals arise from object-tracking over longer spatiotemporal windows than comparable dorsal-stream areas and that V4 signals reflect form transformations at an object level rather than at the level of the local retinal image. We will leverage the percept of long-range apparent motion to probe the role of V4 neurons in motion perception (Aim 1). When a stimulus intermittently skips across the visual field with large spatial and temporal steps, it induces a strong illusory motion percept but neurons in V1 and MT of the dorsal visual stream are strikingly insensitive to the direction of the perceived motion. Psychophysical studies have argued that long-range apparent motion relies not on the dorsal stream but on higher order object tracking processes with large spatiotemporal windows in the ventral visual stream. We will conduct the first neurophysiological investigations in the awake monkey to ascertain the role of V4 in the perception of long- range apparent motion. Next (Aim 2), we will use dynamic stimuli that rotate in the fronto-parallel plane, and translate and rotate in depth, to determine whether V4 neurons encode other common dynamic object transformations (beyond long-range translation), and whether the encoding is based on a sequence of static poses, as in the inferotemporal (IT) cortex, or dynamic transformations. Finally, we will examine the encoding and perception of partially occluded dynamic objects (Aim 3). When an occluded object moves, different parts of the object are revealed over time and integration across time and multiple neuronal receptive fields is required to build an entire object representation. As animals discriminate moving occluded objects, we will study 50-100 neurons with high-density Neuropixels probes. We will use single trial population decoding methods to determine how dynamic stimulus information is integrated across the V4 network to extract object shape and the motion trajectory and how V4 contributes to psychophysical behavior. We anticipate that our results will reveal an important role for V4 in the processing of dynamic stimuli that is complementary to those of MT and IT cortex and will establish the level of internal visual representation operating in V4. Our studies will provide a deeper understanding of the neuronal basis of global motion perception and the tracking of dynamic objects—processes that are impaired in aging populations, especially those with Alzheimer’s disease.