Knowing about people and naming them: can Alzheimer's disease patients do one without the other?

It has recently been suggested that patients with semantic breakdown may show the phenomenon of so-called "naming without semantics". If substantiated, this finding would clearly have a major impact on theories of face and object processing, all of which assume that access to semantic knowledge is a prerequisite for successful naming. In order to investigate this issue, we studied recognition, identification (the ability to provide accurate information), and naming of 50 famous faces by 24 patients with mild to moderate dementia of Alzheimer type (DAT) and 30 age-matched controls. The DAT group was impaired in all three conditions. An analysis of the concordance between identification and naming by each patient, for each stimulus item, established that naming a famous face was possible only with semantic knowledge sufficient to identify the person. Our data support the hypothesis that naming is not possible unless semantic information associated with the target is available. Naming without semantics, therefore, did not occur in patients with DAT. By contrast, there were 206 instances (17% of the total responses) in which the patients were able to provide detailed, accurate identifying information yet were unable to name the person represented. The implication of these findings for models of face identification and naming are discussed.