Color contrast adaptation and compensation in color deficiencies.

Area of Science:

• Vision science
• Color perception
• Sensory processing

Background:

• Anomalous trichromacy (AT) stems from reduced spectral separation between L and M cone photopigments, diminishing sensitivity to LvsM color differences.
• Despite reduced sensitivity, many color-anomalous individuals report color experiences similar to color-normal individuals, implying perceptual compensation mechanisms.

Purpose of the Study:

• To investigate sensory-level compensation in color vision by comparing adaptation aftereffects in color-normal and color-anomalous observers.
• To determine if post-receptoral mechanisms contribute to compensating for reduced LvsM cone signals in anomalous trichromacy.

Main Methods:

• Compared aftereffects of chromatic contrast adaptation in 15 color-normal and 15 color-anomalous observers (10 deutan, 5 protan).
• Quantified adaptation effects by rescaling LvsM contrasts in color-normals to simulate anomalous trichromacy sensitivity losses.
• Assessed if adaptation effects in anomalous observers exceeded predictions based on their threshold sensitivities.

Main Results:

• Deutan observers exhibited adaptation effects exceeding predictions based on threshold sensitivities, indicating partial compensation.
• Protan observers showed mixed results, with less clear evidence of compensation.
• Findings suggest a post-receptoral sensory gain in contrast processing for deutan observers.

Conclusions:

• A post-receptoral sensory gain in contrast processing partially compensates for weaker LvsM cone signals in deutan anomalous trichromacy.
• This compensation mechanism may involve a normalization of contrast coding to adapt to the observer's environment.
• Further research is needed to fully elucidate the sites and mechanisms of perceptual compensation in color vision anomalies.