Instantiation of semantic categories in sentence comprehension by Alzheimer patients

This study examined whether Alzheimer patients can make elaborative inferences based on the semantic context provided by a sentence. More specifically, if presented with the name of a category in a sentence do they, like normals, infer (instantiate) the particular member of that category most appropriate to the meaning of the sentence (e.g., if a sentence mentions a container of juice, do they infer it is a bottle). Patients were presented with a sentence containing the name of a concrete category. The sense of the sentence was consistent with a low-dominant member of that category. Patients were then shown drawings of four members of that category and asked to select the one appropriate to the sentence. They were later asked to name the drawings. If semantic information is degraded in Alzheimer patients for those objects Alzheimer patients cannot name (as has been claimed), then AD patients should be unable to carry out the type of elaborative semantic inference required to instantiate. Results showed that Alzheimer patients were highly accurate at instantiating even objects they could not name. This is consistent with a relative preservation of semantic knowledge about concrete objects in Alzheimer patients.