Semantic abilities in dementia of the Alzheimer type. 1. Lexical semantics.

The lexical semantic abilities of 18 Alzheimer patients were investigated using confrontation naming tasks (including both visual and tactile naming tests) and compared to those of a group of institutionalized, nonneurologically impaired control subjects matched for age, sex, and educational level. The Alzheimer patients produced a greater number of naming errors than the control subjects. The errors made by subjects during the naming tasks were analyzed according to a set of 16 error response types. The Alzheimer patients' response patterns suggest that they do recognize objects which they are unable to name and are able to identify the semantic class to which the target belongs, but cannot provide the lexeme corresponding to the correct individual class member. The results support a semantic network disruption rather than a visual perceptual deficit as the basis of the naming disturbance observed in Alzheimer patients.