Troy J B, Einstein G, Schuurmans R P, Robson J G, Enroth-Cugell C
Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208.
Vis Neurosci. 1989 Sep;3(3):213-23. doi: 10.1017/s0952523800009974.
Perhaps 35% of all of the ganglion cells of the cat do not have classical center-surround organized receptive fields. This paper describes, quantitatively, the responses of two such cell types to stimulation with sinusoidal luminance gratings, whose spatial frequency, mean luminance, contrast, and temporal frequency were varied independently. The patterns were well-focused on the retina of the anesthetized and paralyzed cat. In one type of cell, the maintained discharge was depressed or completely suppressed when a contrast pattern was imaged onto the receptive field (suppressed-by-contrast cell). In the other type of cell, the introduction of a pattern elicited a burst of spikes (impressed-by-contrast cell). When stimulated with drifting gratings, the cell's mean rate of discharge was reduced (suppressed-by-contrast cell) or elevated (impressed-by-contrast cell) over a limited band of spatial frequencies. There was no significant modulated component of response. The reduction in mean rate of suppressed-by-contrast cells caused by drifting gratings had a monotonic dependence on contrast, a relatively low-pass temporal-frequency characteristic and was greater under photopic than mesopic illuminance. If grating of spatial frequency, that when drifted evoked a response from these cells, were instead held stationary and contrast-reversed, the mean rate of a suppressed-by-contrast cell was also reduced and that of an impressed-by-contrast cell increased. But, for contrast-reversed gratings, the discharge contained substantial modulation at even harmonic frequencies, the largest being the second harmonic. The amplitude of this second harmonic did not depend on the spatial phase of the grating, and its dependence on spatial frequency, at least for suppressed-by-contrast cells, was similar to that of the reduction in mean rate of discharge. Our results suggest that the receptive fields of suppressed-by-contrast and impressed-by-contrast cells can be modeled with the general form of the nonlinear subunit components of Hochstein and Shapley's (1976) Y cell model.
猫的所有神经节细胞中，可能有35%没有典型的中心-周边组织化感受野。本文定量描述了两种此类细胞对正弦亮度光栅刺激的反应，光栅的空间频率、平均亮度、对比度和时间频率可独立变化。这些图案清晰地聚焦在麻醉和瘫痪猫的视网膜上。在一种细胞类型中，当对比度图案投射到感受野上时，持续放电会受到抑制或完全被抑制（对比度抑制细胞）。在另一种细胞类型中，引入图案会引发一阵尖峰放电（对比度激发细胞）。当用漂移光栅刺激时，在有限的空间频率范围内，细胞的平均放电率会降低（对比度抑制细胞）或升高（对比度激发细胞）。没有明显的反应调制成分。由漂移光栅引起的对比度抑制细胞平均放电率的降低对对比度呈单调依赖，具有相对低通的时间频率特性，并且在明视觉照度下比中间视觉照度下更大。如果将能引起这些细胞反应的空间频率光栅改为静止并进行对比度反转，对比度抑制细胞的平均放电率也会降低，而对比度激发细胞的平均放电率会增加。但是，对于对比度反转的光栅，放电在偶次谐波频率处包含大量调制，最大的是二次谐波。该二次谐波的幅度不依赖于光栅的空间相位，并且至少对于对比度抑制细胞，其对空间频率的依赖性与平均放电率降低的依赖性相似。我们的结果表明，对比度抑制细胞和对比度激发细胞的感受野可以用霍赫施泰因和沙普利（1976年）Y细胞模型的非线性亚基成分的一般形式来建模。
