Neurolinguistic Approach of Dementia

Memory problems are among the first as well as the most disabling of the cognitive deficits that occur in dementia of the Alzheimer type (DAT). In recent years however, experimental and clincial data have accumulated to support the theoretical assumption that not all kinds of knowledge are stored in the same way. A distinction has been made between episodic and semantic memory. Episodic memory is an autobiographical record of unique episodes and events in an individual’s experience, encoded and maintained in relation to a particular temporal-spatial context. Semantic memory on the other hand is ‘a mental thesaurus, organized knowledge a person possesses about words and other verbal symbols, their meaning and referents, about relations among them, and about rules, formulas and algorithms for the manipulation of these symbols, concepts and relations’ (17). Because the learning of word lists and of paired associates is specifically time- and space-bound, most tests of verbal memory reflect aspects of mainly episodic learning and only to a lesser degree of semantic memory. The examination of semantic memory in DAT, on the other hand, is less well documented and the results of the experiments are still controversial. Bayles (1) concluded that semantic memory in DAT is severely disturbed, whereas Weingartner et al. (18) claimed that it remains normal. Nebes et al. (11) interpreted this controversy as being the result of differences in the degree of automaticity of the examined processes.