Effects of automatic/controlled access processes on semantic memory in Alzheimer's disease.

This study examines the impact of automatic/controlled access processes on the semantic network in 30 patients with Alzheimer's disease (AD). The AD group was compared with a control group using a battery of neuropsychological tests, a variation of Hodges's semantic testing battery, designed to assess semantic knowledge. The AD group had markedly lower scores than the normal group on each semantic test, but with a different degree of deterioration depending on the nature of the processes (controlled/automatic) in accessing the semantic network. AD patients had poorer performances on the explicit semantic tasks mainly involving controlled-process access (e.g., the WAIS Similarities Subtest) than those involving mainly automatic-process access (e.g., the Verbal Automatism test). Analyses of confidence intervals allowed a gradient of impaired performances in increasing order to be elaborated: a) the Verbal Automatism test, b) the WAIS Vocabulary Subtest, c) the WAIS Information Subtest, d) the Letter Fluency Task, e) Naming as a Response to Definition, f) the Category Fluency Task, g) the WAIS Similarities Subtest, and h) the Oral Denomination 80 Test. The results of our study suggest that explicit semantic tasks needing passive or automatic processes to access semantic memory would be better preserved in AD.