Color Agnosia

Definition

Literally, a loss of previous color knowledge.

Current Knowledge

In pure color agnosia, patients have difficulty naming or pointing to named colors, despite relatively preserved color perception (i.e., retaining the ability to match colors or to identify the numbers on the Ishihara plates). They also have difficulty matching colors, either verbally or visually, to familiar colored objects (e.g., identifying the color normally associated with cherries, lettuce, or bananas).

Relatively rare, pure color agnosia must be distinguished from other disturbances of color perception and color naming (color anomia). In color blindness, the individual is unable to perceive or distinguish either certain colors or possibly all color. In the latter case, the world is seen in shades of black and white. While color blindness is usually congenital, it can also be acquired, a condition known as central achromatopsia. The latter is a perceptual deficit thought to result from lesions in the...