Describe the opponent-process theory of color vision and how it explains color afterimages.

Describe the opponent-process theory of color vision and how it explains color afterimages.

• A. The color system uses red-green, blue-yellow, and black-white channels; afterimages arise from fatigue of one antagonistic channel.
• B. Color processing is purely explained by the trichromatic theory.
• C. Afterimages are due to fatigue of rods.
• D. The opponent-process theory operates only at cortical level.

Answer: (A)

Color perception is organized into opponent channels that compare pairs of colors. There are two main chromatic channels: red against green and blue against yellow, plus a luminance (black–white) channel. When you fixate on one color for a while, the neurons in the corresponding opponent channel fatigue and respond less over time. Once you shift your gaze to a neutral field, the fatigued channel signals are reduced, so the opposite color in that pair becomes relatively stronger, producing an afterimage in the complementary color. For example, looking at a red patch fatigues the red–green channel, so you subsequently see a greenish afterimage; looking at blue fatigues the blue–yellow channel, yielding a yellow afterimage. This explains why afterimages occur as complementary colors and ties the phenomenon to how signals are opposed and adapted in the visual system, from retinal processing onward. While initial color detection involves the three cone types, the opponent-processing stage in retinal ganglion cells and beyond is what accounts for the lasting afterimage effect.

Color perception is organized into opponent channels that compare pairs of colors. There are two main chromatic channels: red against green and blue against yellow, plus a luminance (black–white) channel. When you fixate on one color for a while, the neurons in the corresponding opponent channel fatigue and respond less over time. Once you shift your gaze to a neutral field, the fatigued channel signals are reduced, so the opposite color in that pair becomes relatively stronger, producing an afterimage in the complementary color. For example, looking at a red patch fatigues the red–green channel, so you subsequently see a greenish afterimage; looking at blue fatigues the blue–yellow channel, yielding a yellow afterimage. This explains why afterimages occur as complementary colors and ties the phenomenon to how signals are opposed and adapted in the visual system, from retinal processing onward. While initial color detection involves the three cone types, the opponent-processing stage in retinal ganglion cells and beyond is what accounts for the lasting afterimage effect.