Verbal short-term memory deficit in Alzheimer's disease: An examination with the free recall paradigm

To examine the relationship between short-term memory deficit and severity of the dementia in Alzheimer's disease, free recall of word lists was investigated. Twenty-seven patients with diagnosis of probable Alzheimer's disease according to NINCDS-ADRDA criteria, and twelve age-matched controls participated in the study. Patients were divided into two subgroups: fourteen mild and thirteen moderate dementia by Clinical Dementia Rating (CDR). To evaluate short-term and long-term memory components separately, two measures were used: recency effect in the serial-position free-recall curve, and intra-trial retention interval developed by Tulving and Colotla (1970). Mildly demented patients showed a long-term memory deficit with almost normal short-term memory, but moderate ones showed an overall reduction in both measures. These results suggest that memory disorder in Alzheimer's disease changes not only quantitatively but also qualitatively with the progress of dementia, and short-term memory is relatively preserved in the early stage of the disease.