Effects of structural similarity and name frequency on picture naming in Alzheimer's disease.

Impairments to either perceptual or word-retrieval processes have been hypothesized to explain confrontation naming impairments in patients with Alzheimer's disease (AD). This study measured the effects of structural similarity, which affects perceptual processing, and name frequency, which affects word retrieval, on naming latency and accuracy in 16 AD patients and 16 age-matched controls. AD patients named pictures more slowly and made more errors than control participants. Their naming accuracy was disproportionately affected by name frequency, but not by structural similarity. The findings indicate that the processing of structural properties of objects is unaffected in early-stage AD, and suggest that word-retrieval impairments underlie the naming deficit in AD.