Graham N, Sutter A, Venkatesan C
Department of Psychology, Columbia University, New York City, NY 10027.
Vision Res. 1993 Sep;33(14):1893-911. doi: 10.1016/0042-6989(93)90017-q.
Models incorporating spatial-frequency- and orientation-selective channels explain many texture-segregation results, particularly when known nonlinearities are included. One such nonlinearity is complex channels. A complex channel consists of two stages of linear filtering separated by a rectification-type nonlinearity. Here we investigate the spatial-frequency- and orientation-selectivity of simple (linear) channels and of the complex channels' first stage. Observers rated the degree of segregation between two "textures" both composed of elements which were Gabor patches. When the textures differed in type of element (e.g. one composed of vertical and the other of horizontal Gabor patches), the segregation results yield bandwidth estimates for simple channels of approx. 0.5-1.0 octave on the spatial-frequency dimension and 5-20 deg of rotation on the orientation dimension. When the textures differ in the arrangement of elements (e.g. striped vs checkerboard arrangements, both of horizontal and vertical patches), the segregation results yield bandwidth estimates for the first stage of complex channels. These estimates, while differing substantially from one observer to another, were always substantially wider than those for simple channels (by at least a factor of two) but narrower than bandwidths of LGN cells (particularly on the orientation dimension where LGN cells show little selectivity at all).
纳入空间频率和方向选择性通道的模型解释了许多纹理分离结果，特别是当包含已知的非线性时。一种这样的非线性是复数通道。复数通道由两个线性滤波阶段组成，中间隔着一个整流型非线性。在这里，我们研究简单（线性）通道以及复数通道第一阶段的空间频率和方向选择性。观察者对两个均由Gabor斑块元素组成的“纹理”之间的分离程度进行评分。当纹理在元素类型上不同时（例如，一个由垂直Gabor斑块组成，另一个由水平Gabor斑块组成），分离结果得出简单通道在空间频率维度上的带宽估计约为0.5 - 1.0倍频程，在方向维度上的旋转估计为5 - 20度。当纹理在元素排列上不同时（例如，条纹与棋盘格排列，均由水平和垂直斑块组成），分离结果得出复数通道第一阶段的带宽估计。这些估计值虽然在不同观察者之间有很大差异，但总是比简单通道的估计值宽得多（至少两倍），但比外侧膝状体细胞的带宽窄（特别是在方向维度上，外侧膝状体细胞几乎没有选择性）。
