Visual, Spatial and Temporal Filtering and Hyperacuity

视敏度衡量的是眼睛分辨非常微小目标的能力，视敏度受限于眼睛中感光细胞的大小和分布。然而，当位移比正常视力预测的少五倍时，在其他直线上可以检测到轻微的侧向位移中断。这种可分辨性被称为超敏锐度，并且可以通过称为游标位移的刺激来证明，或者通过光栅图案的位移或图案的二分来证明。了解超视敏度对于理解视觉信息处理非常重要，因为超视敏度揭示了视觉在空间中定位的最终精度。该项目将研究眼睛和大脑中信息通道的时空特性如何决定超敏锐度的极限。视觉系统中的单个神经元（神经细胞）具有特定的响应特性，可以优先过滤时间（周期/秒）或空间（例如光栅的周期/度）中的特定频率。超敏锐目标或游标和光栅位移将呈现给人类观察者，然后这些目标将被闪烁照明，或叠加光栅或时空噪声的存在“掩盖”。将对这些不同情况的区别进行比较。为了确定所涉及的神经机制的动态特性，需要测量位移阈值作为亮度对比度、颜色对比度、平均亮度和时间频率的函数。最后，将尝试比较人类的超敏锐表现和猕猴视觉通路中单个神经元的超敏锐能力。这项工作的目标是一个全面的了解神经基础的超敏锐。这种结合心理物理学、生理学和数学建模的方法是罕见而有力的。从神经机制的角度理解这种奇妙的表现，将为理解视觉表现的最终极限提供更好的理论基础。

Visual acuity is a measure of how well the eye can resolve very tiny targets, and is limited by the size and distribution of the photoreceoptor cells in the eye. However, a slight sideways displacement break in an otherwise straight line can be detected when the displacement is as much as five times less than the normal acuity would predict. This discriminability is known as hyperacuity, and can be demonstrated by this stimulus called vernier displacement, or by displacement of a grating pattern or by bisection of a pattern. Understanding hyperacuity is important for understanding visual information processing because hyperacuity reveals the ultimate precision of visual localization in space. This project will study how spatial and temporal properties of information channels in the eye and brain determine the limits of hyperacuity. Single neurons (nerve cells) in the visual system have particular response properties that preferentially filter particular frequencies in time (cycles/sec) or space (cycles/degree, of a grating, for example). Hyperacuity targets or vernier and grating displacement will be presented to human observers, and then these targets will be "masked" by the presence of flickering illumination, or superimposed gratings, or spatiotemporal noise. The discriminations will be compared for these different cases. To determine the dynamic characteristics of the neural mechanisms involved will require measurement of displacement thresholds as a function of luminance contrast, color contrast, mean luminance, and temporal frequency. Finally, a comparison will be attempted between human hyperacuity performance and the hyperacute capabilities of single neurons in the macaque monkey's visual pathway. The goal of this work is a comprehensive understanding of the neural basis for hyperacuity. The approach combining psychophysics, physiology and mathematical modelling is rare and powerful. Understanding this wonderful performance in terms of neural mechanisms will lead to a better theoretical basis for understanding the ultimate limits of visual performance.