Event-related potentials (ERPs) during repetition priming in Alzheimer's patients and young and older controls

Although memory tested explicitly (e.g., recognition) is clearly deficient in the early stages of Alzheimer's disease, it is less clear if memory tested implicitly is similarly affected. To assess this, event-related potentials (ERPs) were recorded during a word-repetition priming paradigm, with semantic and orthographic orienting tasks, from 10 patients with mild probable Alzheimer's disease (PAD; mean age of 70.6), 10 young (24.1) and 10 older (69.8) controls. The extent of priming by word repetition was assessed using the new minus old ERP repetition effect. The young and older control groups showed clear ERP repetition effects that were larger during semantic than orthographic blocks. Although the PAD patients displayed the same general trends, their ERP repetition effects were not nearly as marked when compared to controls. To the extent that the ERP repetition effect recorded during this repetition priming paradigm is a measure of implicit performance, the data suggest that memory assessed in this fashion is spared in at least some Alzheimer's patients in the early stages of the disease.