Semantic dementia: Autobiographical contribution to preservation of meaning

Abstract

Five patients with a progressive semantic disorder were noted to produce a surprising range of nominal terms in their everyday conversation in contrast to their grossly impaired naming and word comprehension on formal tests. It was hypothesised that since general conversation revolves around autobiographical topics, a key factor in preservation of vocabulary might be the relevance of concepts to personal experience. The possible contribution of direct experience in maintenance of both verbal and nonverbal meaning was evaluated in three experiments, involving identification of (1) names of people; (2) names of places; and (3) objects. Patients performed consistently better for personally relevant than for nonpersonal names and places, a pattern of findings not seen in a control group of amnesic Alzheimer patients. Moreover, a study of object recognition in one patient revealed superior recognition for her own compared to alternative examples of the same object. The findings highlight the role of autobiographical experience in the maintenance of meaning, and underline the interrelationship between “episodic” and “semantic” knowledge.