Progressive loss of access to spoken word forms in a case of Alzheimer's disease.

We report the results of a longitudinal study of a progressive anomia in a patient with dementia of the Alzheimer type (DAT). The anomia cannot be attributed to a deficit within the semantic system, but appears instead to arise from impaired access to the phonological lexicon at a post-semantic stage of the naming process: a deficit that hitherto has not been reported in DAT. Specific naming responses were affected consistently by the disorder, showing that disorders of access are not invariably associated with inconsistent responding. Before specific responses disappeared from spontaneous use, there appeared to be an intervening stage at which some responses could be elicited by an initial phoneme cue, suggesting a low level of spontaneous activity of insufficient strength to elicit a response unaided. The frequency of the name affected naming performance, but did not appear to interact with the severity of the naming disorder, suggesting that the parameters of the normal naming system were unaffected. It is claimed that important new insights into the characteristics of progressive anomia have been obtained by taking a longitudinal approach.