ABSTRACT
A number of additional terms have been used to identify various problems in visual gnosis. They are often used indiscriminately, the same term used to identify slightly or completely different problems. Many names have been given to a single problem. Many other problems hinder the investigation of visual gnosis disorders. For instance, a variety of totally different pathologies can produce a single visual gnostic disorder coupled with widely divergent neighborhood signs. Disorders of visual gnosis are often ignored in the evaluation of other serious behavioral disorders. Three distinct varieties of color vision disturbances are recognized —achromatopsia, color agnosia, and anomia for colors. Clinical differences in the three are significant for understanding the processing of color identification. This category is frequently combined with color agnosia, both being called color anomia or color naming defect. The color naming defect is almost always associated with other evidence of aphasia which may range from a mild anomia to a well developed posterior aphasia.
