Degree of cognitive impairment and the dissociation of implicit and explicit memory.

One group of normal elderly adults and two groups of cognitively impaired elderly adults were compared on an implicit and an explicit memory task. Degree of impairment affected explicit memory; the mildly and moderately impaired elderly adults demonstrated significantly reduced recognition performance. Degree of impairment also affected implicit memory priming performance, particularly for low frequency items, as measured by a word completion task. Explicit memory performance declined for both cognitively impaired groups, but implicit memory performance was sensitive to the degree or severity of impairment, causing a decline in performance only in the moderately impaired group.