Stockman Andrew, Henning G Bruce, Anwar Sharif, Starba Robert, Rider Andrew T
UCL Institute of Ophthalmology, University College London, London, UK.
J Vis. 2018 Feb 1;18(2):6. doi: 10.1167/18.2.6.
Cone signals in the luminance or achromatic pathway were investigated by measuring how the perceptual timing of M- or L-cone-detected flicker depended on temporal frequency and chromatic adaptation. Relative timings were measured, as a function of temporal frequency, by superimposing M- or L-cone-isolating flicker on "equichromatic" flicker (flicker of the same wavelength as the background) and asking observers to vary contrast and phase to cancel the perception of flicker. Measurements were made in four observers on up to 35 different backgrounds varying in wavelength and radiance. Observers showed substantial perceptual delays or advances of L- and M-cone flicker that varied systematically with cone class, background wavelength, and radiance. Delays were largest for M-cone-isolating flicker. Although complex, the results can be characterised by a surprisingly simple model in which the representations of L- and M-cone flicker are comprised not only of a fast copy of the flicker signal, but also of a slow copy that is delayed by roughly 30 ms and varies in strength and sign with both background wavelength and radiance. The delays, which are too large to be due to selective cone adaptation by the chromatic backgrounds, must arise postreceptorally. Clear evidence for the slow signals can also be found in physiological measurements of horizontal and magnocellular ganglion cells, thus placing the origin of the slow signals in the retina-most likely in an extended horizontal cell network. Luminance-equated stimuli chosen to isolate chromatic channels may inadvertently generate slow signals in the luminance channel.
通过测量M或L视锥细胞检测到的闪烁的感知时间如何依赖于时间频率和颜色适应，对亮度或非彩色通路中的视锥细胞信号进行了研究。通过将M或L视锥细胞隔离闪烁叠加在“等色”闪烁（与背景波长相同的闪烁）上，并要求观察者改变对比度和相位以消除闪烁感知，来测量作为时间频率函数的相对时间。在四名观察者身上，对多达35种不同波长和辐射度的背景进行了测量。观察者表现出L和M视锥细胞闪烁的显著感知延迟或提前，其随视锥细胞类型、背景波长和辐射度而系统变化。M视锥细胞隔离闪烁的延迟最大。尽管结果很复杂，但可以用一个惊人简单的模型来描述，其中L和M视锥细胞闪烁的表征不仅包括闪烁信号的快速副本，还包括一个延迟约30毫秒的慢速副本，其强度和符号随背景波长和辐射度而变化。这些延迟太大，不可能是由于彩色背景对视锥细胞的选择性适应造成的，一定是在感受器后产生的。在水平细胞和大细胞神经节细胞的生理测量中也能找到慢速信号的明确证据，因此将慢速信号的起源置于视网膜中——最有可能在一个扩展的水平细胞网络中。为隔离颜色通道而选择的亮度等效刺激可能会无意中在亮度通道中产生慢速信号。
