Quantitative characterization of verbal learning deficits in patients with Alzheimer's disease.

The performance of patients with Alzheimer's Disease (AD) was compared to that of normal controls (NCs) on a free recall rote learning task involving a list of words (California Verbal Learning Test). Exponential learning functions were fitted to the observed data of the two groups. These learning functions provided estimates for the rate of learning and the theoretically expected upper limit of recall performance in each group. The rate constant of learning was higher in AD patients than in NCs, indicating less distributed learning across the given trials. The expected upper limit of recall performance was lower in AD patients than in NCs. Results suggest that AD patients benefit less from the repetition of information at the time of encoding.