The Von Restorff effect in ageing and Alzheimer's disease

The purpose of the study was to evaluate the Von Restorff effect in normal ageing and in Alzheimer's disease (AD). A shortened paradigm was administered to three groups of subjects: young volunteers, elderly volunteers and patients with early-stage AD (MMSE>20). Each subject was presented with 25 lists of 10 words each, the target word appearing in double font size. A free recall phase followed the presentation of each list; after completion of the battery, a size recognition test was administered and subjects were inquired regarding the strategy employed and perception of target words. The total number of recalled words differed significantly among the three groups (young volunteers 144.4+/-38.6, elderly volunteers 86.5+/-17.6, patients 44.2+/-14.6). A significant difference in percentage of recall was found between target and non-target words in young (60.0+/-13.8% vs. 45.7%+/-15.0%, p<0.001) and in elderly (31.2+/-11.4% vs. 20.2+/-6.9%, p<0.001) volunteers, but not in patients (10.7+/-6.9% vs. 11.8+/-7.3%). The present study highlights that the Von Restorff effect can be detected in healthy elderly subjects, and that it is significantly reduced in patients in the early stage of AD. On the basis of the findings of the present study it is not possible to disentangle the contribution of visual-perceptual and encoding impairment, both of them potentially contributing to the observed reduction.