The effects of prolonged temporal modulation on the differential response of color mechanisms

The identification of three independent cardinal directions in color space suggests the existence of three independent post-receptoral mechanisms that can be desensitized by habituation to a temporally modulated light. In this paper, the differential response of each cardinal mechanism is estimated over a range of inputs before and after habituation. Simple mathematical considerations show that the threshold elevations following temporal modulation are not consistent with multiplicative gain changes; rather, these elevations require a change in the shape of each cardinal mechanism's response function. With this method, the effects of habituation can also be differentiated from the effects of a change in the steady adapting light.