Bell Jason, Gheorghiu Elena, Hess Robert F, Kingdom Frederick A A
McGill Vision Research, Dept. of Ophthalmology, McGill University, 687 Pine Av. West, H4-14, Montreal, Quebec, Canada H3A 1A1.
Vision Res. 2011 Aug 1;51(15):1760-6. doi: 10.1016/j.visres.2011.06.003. Epub 2011 Jun 16.
Radial Frequency (RF) patterns can be used to study the processing of familiar shapes, e.g. triangles and squares. Opinion is divided over whether the mechanisms that detect these shapes integrate local orientation and position information directly, or whether local orientations and positions are first combined to represent extended features, such as curves, and that it is local curvatures that the shape mechanism integrates. The latter view incorporates an intermediate processing stage, the former does not. To differentiate between these hypotheses we studied the processing of micro-patch sampled RF patterns as a function of the luminance polarity of successive elements on the contour path. Our first study measures shape after effects involving suprathreshold amplitude RF shapes and shows that alternating the luminance polarity of successive micro-patch elements disrupts adaptation of the global shape. Our second study shows that polarity alternations also disrupt sensitivity to threshold-amplitude RF patterns. These results suggest that neighbouring points of the contour shape are integrated into extended features by a polarity selective mechanism, prior to global shape processing, consistent with the view that for both threshold amplitude and suprathreshold amplitude patterns, global processing of RF shapes involves an intermediate stage of processing.
径向频率（RF）模式可用于研究对熟悉形状（如三角形和正方形）的处理。对于检测这些形状的机制是直接整合局部方向和位置信息，还是局部方向和位置首先被组合以表示扩展特征（如曲线），而形状机制整合的是局部曲率，目前存在分歧。后一种观点包含一个中间处理阶段，前一种观点则没有。为了区分这些假设，我们研究了微补丁采样RF模式的处理，它是轮廓路径上连续元素的亮度极性的函数。我们的第一项研究测量了涉及超阈值幅度RF形状的形状后效应，并表明交替连续微补丁元素的亮度极性会破坏全局形状的适应性。我们的第二项研究表明，极性交替也会破坏对阈值幅度RF模式的敏感性。这些结果表明，在全局形状处理之前，轮廓形状的相邻点通过极性选择机制被整合到扩展特征中，这与以下观点一致：对于阈值幅度和超阈值幅度模式，RF形状的全局处理都涉及一个中间处理阶段。
