Does the sluggishness of colour perception reflect a limitation in the maximum (slew) rate at which chromatic pathways respond to changes in colour?

在较高的时间频率下，闪烁光的出现是由一个稳定的平均值主导的，在闪烁频率处有一些残留的干扰。快速关闭和缓慢打开的闪烁灯和缓慢打开和快速关闭的闪烁灯的平均外观可能非常不同，即使它们的平均颜色和强度相同。（我们把这些波形称为“锯齿”刺激。）这些意想不到的差异很重要，因为它们可以为编码颜色的视觉信号的潜在处理提供独特的见解。我们最初的假设是，这些差异是由于颜色机制能够更好地跟随缓慢的颜色变化而不是快速的颜色变化。结果，它们的平均输出向缓慢变化的方向倾斜。例如，一个反复缓慢变红但又迅速变绿的黄灯看起来比一个快速变红但缓慢变绿但看起来更绿的灯平均更红。这种不平衡与许多当前的色彩处理模型不一致，但可以用我们的模型来解释。具体来说，我们认为颜色机制发出颜色变化信号的速率被限制在一个特定的水平上。如果变化率超过该水平，则输出仅在极限变化率下变化。我们称之为“慢速”模式。虽然回转速率限制的概念在电子学中很常见（例如在运算放大器的规范中），但据我们所知，它在视觉研究领域是新颖的。我们提出了一系列的实验，旨在测试和发展回转率模型。将进行色检测和色辨别的测量，以表征锯齿波形的斜率随各种刺激参数的变化所产生的影响。在每个阶段，这些结果将与由计算机模拟的回转速率模型所产生的预测结果进行比较。我们的目标是批判性地评估回转率模型。模型能在多大程度上解释数据？对模型的简单修改能更好地解释数据吗？是否可以使用其他类型的波形来严格测试模型？计算机模拟能提示其他实验吗？除了引起锯齿波的平均颜色的变化外，有限的慢速也应该使我们对闪烁不那么敏感。因此，众所周知的颜色感知迟缓可能是由于慢速限制，而不是更传统的解释，即颜色信号随时间平均。我们还将通过比较闪烁灵敏度测量值和锯齿测量值来测试这一预测。测试慢速模型本身不一定是这个提议最关键的特征。同样重要的是，我们正在使用非常规的刺激和非常规的模型和方法生成一个新的数据集。这个新的数据集将提供给其他研究人员，并且可以被该领域的其他人以及我们自己使用，以生成颜色视觉如何工作的新模型。该提案的主要目标是更多地了解人类大脑如何处理彩色信号，特别是为什么彩色信号的处理速度比消色信号慢得多。尽管最近在相关领域取得了许多进展，但关于人类色彩处理工作的细节仍然知之甚少。

At higher temporal frequencies, the appearance of flickering lights is dominated by a steady average, with some residual disturbance at the flicker frequency. The average appearances of flickering lights that turn rapidly off and slowly on and those that turn slowly on and rapidly off can be very different even when their mean colours and intensities are the same. (We refer to these waveforms as 'sawtooth' stimuli.) These differences, which are unexpected, are important because they can provide unique insights into the underlying processing of visual signals that encode colour. Our initial hypothesis is that the differences are due to chromatic mechanisms being better able to follow slow colour changes than fast ones. As a result, their mean outputs become skewed in the direction of the slow change. For example, a yellow light that repeatedly changes slowly to red but then rapidly to green looks on average more red than a light that changes rapidly to red but slowly to green, which looks more green. This imbalance is inconsistent with many current models of chromatic processing, but can be explained by our model. Specifically, we propose that the rate at which colour mechanisms can signal changes in colour is limited to a particular level. If the rate of change exceeds that level, the output varies only at the limiting rate of change. We call this the 'slew-rate' model. Although the idea of a slew-rate limit is familiar in electronics (for example in the specification of operational amplifiers), it is as far as we know novel in the field of vision research. We propose a series of experiments that are designed to test and develop the slew-rate model. Measurements of chromatic detection and chromatic discrimination will be made to characterize the effects of changing the slopes of the sawtooth waveforms as a function of various stimulus parameters. At each stage, these results will be compared with predictions generated by computer simulations of the slew-rate model. Our goal is to critically evaluate the slew rate model. To what extent can the model account for the data? Can simple modifications to the model better account for the data? Can other types of waveforms be used to critically test the model? Can computer simulations suggest other experiments? In addition to causing changes in the mean colour of sawtooth waveforms, a limiting slew-rate should also make us less sensitive to flicker. Thus, the well-known sluggishness of colour perception may be due to the slew-rate limit rather than the more conventional explanation that colour signals are averaged over time. We will also test this prediction by comparing flicker sensitivity measurements with the sawtooth measurements. Testing the slew-rate model per se is not necessarily the most critical feature of this proposal. Equally critical is the fact that we are generating a new dataset using unconventional stimuli and an unconventional model and approach. This new dataset will be made available to other researchers, and can be used by others in the field as well as ourselves to generate new models of how colour vision works. The primary goal of this proposal is to understand more about how chromatic signals are processed in the human brain and in particular why chromatic signals are processed much more slowly than achromatic ones. Despite the many recent advances in related fields, details about how colour processing in humans work remains relatively little understood.