Verbal and nonverbal short‐term memory in patients with Alzheimer's disease and in healthy elderly subjects

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Abstract
Short‐term memory (STM) deteriorates with the progression of Alzheimer's disease (AD). The purpose of the present study was to characterize this decline by examining component processes of STM. Accordingly, AD patients whose dementia ranged from mild to severe and healthy, age‐matched subjects received the Brown‐Peterson distractor task, in which class of material (verbal and nonverbal), number of memoranda (one, two, and three), and agent of forgetting (time and distraction) were manipulated. Healthy elderly subjects showed the expected pattern of performance: When distraction was present, forgetting was greater with longer retention intervals and larger memory loads; when distraction was absent, recall was perfect. AD patients showed significant forgetting at shorter intervals and with smaller memory loads than healthy elderly subjects when distraction was present; without distraction, AD patients' recall of nonverbal (but not verbal) material was impaired, which may be attributable to the greater difficulty of the nonverbal task over the verbal one and to a diminished rehearsal capacity of AD patients for nonverbal material. Data from individual patients suggest that the verbal and nonverbal systems can deteriorate independently.

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