Neural bases of color-specific semantic loss: Two cases of object-color knowledge impairment.

Human color processing includes perception, naming, and knowledge of colors. These facets are dissociable from each other and appear to have discrete neuronal bases. Here, we present two cases with loss of object color knowledge but spared color perception and knowledge of object other than color. Case 1, a stroke patient with lesions in the left medial occipitotemporal lobe, is impaired in associating colors or color names with objects or object names. However, he demonstrated good color perception and well-preserved knowledge of object form, size, and functions. Case 2, another stroke patient with a lesion in the left fusiform and lingual gyri, showed anomia for colors and slight impairment in object color knowledge. Case 1 is the first subject to have complete loss of object color knowledge, including the verbal association between object and color names without impairment in object knowledge about perceptual properties other than color. These results indicate that color and object processing is comprised of numerous dissociable features with distinct neuronal bases. Further, they provide evidence supporting the critical role played by the left medial occipitotemporal region in color knowledge.