Fluency performance patterns in Alzheimer's disease and Parkinson's disease

This study compared 38 patients with Alzheimer's disease, 20 patients with Parkinson's disease, and 51 normal controls on nonverbal, semantic, and pho nological fluency tasks. Semantic and nonverbal fluencies declined signific antly with age. The AD group was impaired on all fluency measures, with the greatest impairments on nonverbal and semantic fluency. The PD group was i mpaired on nonverbal and semantic fluencies. Differences observed in semant ic fluency between the AD and PD groups could not be accounted for by demen tia severity. Motor disability did not account for the PD nonverbal fluency deficit. This study provides evidence for a semantic-based impairment in A D and suggests that PD fluency deficits are primarily cognitive rather than motor in nature.