Semantic Memory Loss in Dementia of Alzheimer's Type

Abstract

This paper examines three methodological issues concerning the measurement of semantic memory impairment in brain-damaged patients. Ten carefully selected patients with dementia of Alzheimer's type (DAT) and anomia were studied. A battery of perceptual tests and direct tests of semantic memory led to the conclusion that these patients represented a homogeneous group having a prominent deterioration of their semantic memory store without visual perceptual deficits. The first issue addressed in this patient group was whether verbal fluency impairment accurately reflected the loss of semantic memory. It was found that verbal fluency (generation of semantic category lists) was impaired due to two major constraints: deterioration of semantic memory store, and variable difficulties in semantic search. Verbal fluency, therefore, reflects semantic memory loss to some degree, but is not a direct test of semantic memory store in DAT. The second issue was whether semantic memory impairment in our patients conformed to the 'semantic storage disorder' syndrome hypothesized by Shallice (1987). It was shown that, consistent with this hypothesis, the patients demonstrated co-occurrence of consistency of errors, loss of semantic cueing, and preserved superordinate knowledge with loss of detailed knowledge of concept items. The third issue was whether semantic cueing and semantic priming are altered in a similar manner in DAT. It demonstrated that semantic cueing and semantic priming, using the same words whose concepts were degraded in semantic memory, yielded an entirely different pattern of results. Cueing and priming therefore may not be used interchangeably in the study of semantic loss after brain damage.

A longitudinal study of semantic memory impairment in patients with Alzheimer’s disease

“…In a seminal study, Chertkow and Bub (1990) used an item-to-item specific test and observed error consistency across test trials, providing support for the degraded store view. In this study, the patients were first asked to name pictures and subsequently to perform a "same category word to picture matching" task.…”

Early-onset and late-onset Alzheimer's disease are associated with distinct patterns of memory impairment

“…Impairment in delayed recall seems to be one of the best predictors of future dementia (Small et al, 2000;Ivanoiu et al, 2005). Semantic memory, which concerns general world knowledge, is also impaired in AD, even at the pre-dementia stages of the disease (Chertkow and Bub, 1990;Duong et al, 2006;Joubert et al, 2010).…”

“…Semantic deficits have been documented in AD using a variety of standard clinical neuropsychological tests (Huff et al, 1986;Rosser and Hodges, 1994;Hodges and Patterson, 1995;Adlam et al, 2006) and using more specific measures (Chertkow and Bub, 1990;Hodges et al, 1992;Greene and Hodges, 1996;Fung et al, 2001;Thompson et al, 2002;Whatmough et al, 2003;Joubert et al, 2010). Working memory deficits are also frequently reported in AD and involve reduced span for words, digits, letters and spatial locations (Grossi et al, 1993;Belleville et al, 1996).…”

Neuropsychological strategies for detecting early dementia

“…Compared with normal subjects, AD patients generate significantly fewer members of common semantic categories (Canning et al, 2004;Graham et al, 2004;Lipton et al, 2003, Monsch et al, 1994Salmon et al, 1999), a result either of the loss of semantic information or its disorganization (e.g., Chertkow & Bub, 1990;Grober et al, 1985;Martin & Fedio, 1983).…”