Abstract

Examined script and lexical retrieval in 29 patients (mean age 64.07 yrs) with probable dementia of the Alzheimer's type (DAT), 14 matched depressed patients, and 31 matched normal controls. DAT Subjects' breakdown in script production was structurally similar to their impaired lexical retrieval such that script events of low frequency and low centrality value were lost first. DAT Subjects also produced more events that fell outside the script boundary and more event-order errors. Four cases with DAT were identified on the basis of Z scores whose script production was at least 2 standard deviations greater than their lexical production or vice versa. This finding suggests that it may be possible to dissociate script and lexical knowledge and production processes. Findings lend partial support for a model of knowledge representation that includes parallel and partially redundant memory networks that are distinctly distributed in the brain.