Not So Trivial Pursuit

Semantic memory increases initially in Alzheimer's disease and certain dementias: here's why

(RxWiki News) Semantic memory is the ability to recall seemingly trivial facts such as knowing what a refrigerator looks like. Semantic memory allows us to recall general knowledge.

In semantic dementia, however, these capacities diminish.

The deterioration of semantic memory is also a characteristic of Alzheimer's disease. Now researchers have determined the elements of semantic memory which are the first to deteriorate, possibly explaining why hyper semantic priming can be seen in the early stages of Alzheimer's disease. Semantic priming is the ability to recognize a word (i.e., "lion") after seeing a related word (i.e.,"tiger").

Surprisingly, a previous study found semantic priming to actually increase in the early stages of Alzheimer's disease, resulting in so-called hyperpriming. (In later stages of the disease, however, this ability greatly diminishes.)

Dr Mickaël Laisney and colleagues from the university hospitals of Caen and Rennes studied word recognition in 16 Alzheimer's patients and 8 semantic-dementia patients. Participants were shown pairs of words and asked to indicate whether they recognized the second word in each pair.

In the new study, researchers found that the first elements of semantic memory to deteriorate are the distinguishing characteristics of a concept, such knowing what a refrigerator looks like. This effect blurs closely related concepts so that, for example, refrigerators and freezers become the same thing in patients' minds. The authors suggest this to be the reason why patients temporarily find it easier to recognise related words in the early stages of memory loss.

This effect disappears in more advanced stages of both diseases.

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Review Date: 
December 21, 2010