Impaired retrieval of object-colour knowledge with preserved colour naming.

Two cases (G.G. and A.V.) are described of cognitive impairment resulting from herpes simplex infection. Both cases demonstrated anomic disorders and impairments in drawing but only in G.G.'s drawings was there a reliable selective impairment for items from natural categories. Both cases, however, showed an impairment for the retrieval of knowledge concerning the colours of objects. The impairment has, in the past, been ascribed to interference from colour anomia; this was not so for the present cases. For G.G. and A.V., impairments in object-colour retrieval were related to errors in picture naming. More errors were associated with items that induced circumlocutions than to those that were correctly named. The impairment was also present for some items that were named correctly. The patients' impairments are discussed within a model in which object-colour knowledge is functionally situated between an object's shape description and its output phonology but on a separate route from other associated object knowledge.