Episodic memory in dementia of the Alzheimer type and in normal ageing: similar impairment in automatic processing.

A perceptual identification task was used to provide an implicit measure for automatic memory processes. The facilitation of word identification on repeated presentation is taken as a measure of the automatic retrieval of an episode. In addition, recognition memory was tested. The recognition task is an explicit test of memory and relies mainly on controlled processing. In the first experiment 11 patients suffering from probable Alzheimer disease and 11 normal age- and sex-matched controls were tested. Both groups exhibited a rather small facilitation effect (ca 7%) but did not differ in the size of the effect. However, when tested explicitly, a difference in recognition memory existed between the two groups. In the second experiment the performance of 11 normal young subjects was compared to that of 11 normal elderly subjects. Whereas the elderly group showed a small facilitation effect similar to that observed in the first experiment, a considerable facilitation effect was found for the young group. Also, the elderly group had poorer recognition memory than the young group.