Inhibition of visual and conceptual information during reading in healthy aging and Alzheimer's disease.

The present experiment examined the effect of distraction on reading ability and comprehension in healthy aging and early stage dementia of the Alzheimer type (DAT). A modified version of the reading task used by Connelly, Hasher, and Zacks (1991, Experiment 2) was employed. Healthy young, healthy old (60-79 years, and 80 years and over), very mild DAT, and mild DAT participants read passages aloud and then answered comprehension questions. There were four experimental conditions in which distracting information was embedded in the text: (control), orthographic (xxxxx), lexical (unrelated), and semantic (related). The results indicated that there was greater susceptibility to increasing levels of distraction with age and increasing dementia severity. Moreover, there was a substantial slowdown in reading time in mild DAT when text was used as distracting information, especially conceptually related text. Furthermore, mild DAT participants were more likely to make false alarms in comprehension performance (i.e., choose as an answer the incorrect response which contained the related distracting information). Thus, in early stage DAT, there appears to be increased difficulty inhibiting partially activated information, especially when it is related to the relevant information being processed.