Performance of Alzheimer's disease patients in judging word relatedness.

Sixty individuals with probable Alzheimer's disease (AD) and 48 normal elders were given a task in which they had to judge the relatedness of concepts as a means of evaluating semantic memory. Very mild AD patients performed similarly to normal elders. Mild AD patients were significantly inferior in performance to normals but the pattern of their performance did not suggest a loss of conceptual knowledge. Moderate AD patients were significantly inferior in performance to mild AD patients, and 8 moderate AD patients (compared to 1 mild AD patient) were unable to do the task. The pattern of performance of moderate patients suggests that conceptual knowledge may degrade and ultimately be lost.