The nature of lexical-semantic impairment in Alzheimer's disease

Semantic-lexical disorders of Alzheimer's disease (AD) patients have been considered by various authors as resulting either from a loss of information or from an inability to access an intact semantic representation. Since consistency of errors over the same items is usually considered as a proof of the "loss of information" hypothesis, 15 AD patients and 10 age-matched normal controls received a confrontation naming task and a "verbal associates recognition" task, constructed using the same set of stimuli. For each stimulus to be named, the patient received a list of associates, belonging to different associative categories (superordinate, part of whole, attribute, function associate, functional context and contrast coordinate); his task consisted in judging if the word was or was not related to the target. The working hypothesis was that, if naming errors of demented patients are due to a loss of information in the semantic representation of the not-named items, then these patients should perform worse with the semantic associates of the not-named than with those of the correctly named items. Results confirmed the hypothesis in AD patients with moderate anomia, showing that, in the early stages of the demential dissolution, naming errors can be traced back to a loss of information at the level of the semantic representation subtending the misnamed items. © 1990.