On the nature of the verbal memory deficit in Alzheimer's disease.

Verbal memory was investigated in patients with Alzheimer's disease (AD) with previously documented deficits in word production and comprehension. Procedures were employed to evaluate word recall and recognition within the context of both "multistore" and "levels of processing" models of memory. In addition, memory abilities were evaluated with respect to performance on measures of verbal fluency and language comprehension. As expected, the AD patients performed significantly worse than normal individuals on all tasks. However, in each experiment their pattern of recall across conditions was found to be qualitatively similar to that produced by normal subjects. It was argued that the memory impairment associated with Alzheimer's disease may be largely due to an inability to encode a sufficient number of stimulus features or attributes. Furthermore, this encoding deficit includes, but is not limited to, semantic attributes. Similarities between the performance of the AD patients and reported findings with Korsakoff patients and normal subjects with "weak" memory were discussed.