Anosognosia for memory impairment in Alzheimer's disease

Objective: To investigate whether patients with Alzheimer's disease (AD) were able to alter their awareness of memory deficits after exposure to a memory task.

Methods: Thirty normal older adults and 23 mild AD patients participated in the study. Anosognosia was assessed using discrepancies between self- and informant-evaluations of cognitive and functional performance. Participants estimated their performance on the Verbal Paired Associates task at different points in time (before, immediately after the task and after a 1-h delay).

Results: AD patients were generally less able to judge their memory abilities than healthy older adults, and tended to overestimate their task performance beforehand. Their prediction accuracy increased immediately after the task, but after a 1-h delay, they again misjudged their abilities at pretesting accuracy levels. Self-carer discrepancy scores of awareness of deficits in memory and other areas correlated significantly with memory tests but not with other neuropsychological tasks in the assessment, and larger discrepancy scores were associated with poorer performance.

Conclusion: AD patients can monitor their task performance online, but are unable to maintain awareness of their deficits over time. Loss of awareness of memory deficits (or of any other deficits) in early stage AD may indicate damage to a system which updates a personal knowledge base with recent information. Failure to retain this information impedes abstraction from episodic to semantic memory.