Rates of forgetting in Alzheimer-type dementia and Korsakoff's syndrome.

After initial learning had been equated as closely as possible, 16 Alzheimer-type dementing patients showed the same rate of forgetting on a picture recognition test administered at intervals over the course of a week as 16 Korsakoff patients and 16 healthy controls. This suggested that the anterograde amnesic deficit in both Alzheimer's disease and Korsakoff's syndrome is primarily an acquisition or learning deficit. The Alzheimer patients differed from both the Korsakoff patients and the healthy controls in showing diminished digit span and severely impaired performance at the Brown-Peterson test, implicating a deficit of short-term (or working) memory. The variability of performance within groups on the principal tests employed was also examined; and the Alzheimer results are discussed with respect to the underlying neuropathology, and the implication for pharmacotherapy.