Semantic memory impairment in Alzheimer's disease: failure of access or degraded knowledge?
A battery of neuropsychological tests designed to assess semantic knowledge about the same items both within and across different modalities was administered to a group of 22 patients with dementia of the Alzheimer type (DAT) and 26 matched controls. The DAT patients were impaired on tests of category fluency, picture naming, spoken word-picture matching, picture sorting and generation of verbal definitions. A relative preservation of superordinate knowledge on the sorting and definition tests, as well as a disproportionate reduction in the generation of exemplars from lower order categories was noted. Analysis of the errors made by each patient across the different tests, revealed a significant correspondence between the individual items. These findings offer compelling evidence that the semantic breakdown in DAT is caused by storage degradation.
Hodges
J R
JR
University of Cambridge Clinical School, U.K.
Salmon
D P
DP
Butters
N
N
D000368:Aged; D000544:Alzheimer Disease / Q000175:diagnosis / Q000523:psychology*; D000849:Anomia / Q000175:diagnosis / Q000523:psychology; D005260:Female; D006801:Humans; D008297:Male; D011939:Mental Recall; D009483:Neuropsychological Tests; D010153:Paired-Associate Learning; D011446:Prospective Studies; D011930:Reaction Time; D012153:Retention, Psychology; D012660:Semantics; D014706:Verbal Learning