The role of premorbid expertise on object identification in a patient with category-specific visual agnosia.

The role of premorbid expertise in object identification was investigated in the category-specific visual agnosia patient ELM. For several years prior to his stroke ELM played bugle in a military band. We surmised that band membership would lead to preferential exposure to, and expertise for, brass instruments relative to other musical-instrument families. To test this hypothesis we assessed ELM's musical instrument identification capability for brass and stringed instruments. Testing was conducted 14 years post-stroke. ELM listed significantly more correct attributes for five brass instruments than for five stringed instruments. On a picture-word matching task ELM showed significantly better identification of brass, relative to stringed, musical instruments. Finally, when ELM was required to pair novel shapes with labels denoting brass or stringed instruments, he made significantly more errors in the stringed-instrument condition than in the brass-instrument condition. We conclude that the elevated attribute knowledge accompanying expertise serves to increase the visual and semantic distance between objects within a category, thereby protecting them against identification deficits in the context of category-specific visual agnosia.