EVIDENCE FOR AN IMPAIRED ABILITY TO DETERMINE SEMANTIC RELATIONS IN ALZHEIMERS-DISEASE PATIENTS

An important feature of Alzheimer's disease (AD) that differentiates i t from normal aging is the deterioration of semantic memory. The purpo se of this study was to determine if the poor performance of AD patien ts on tasks that require them to use semantic memory is related to the ir inability to identify specific semantic relations. This hypothesis was tested by comparing the reaction times and error rates of AD patie nts to those of the normal elderly and normal young in a sentence veri fication task. We found that AD patients were significantly slower and less accurate than the normal elderly and the young on aspects of the task that required the knowledge of specific semantic relationships. In a 2nd experiment, young normal participants performed the same task with a concurrent memory load. The results from Experiment 2 indicate that the performance of AD patients in this task cannot be attributed to a diminished working memory capacity.