Pictorial and lexical priming: Patterns of implicit memory in Alzheimer's and Parkinson's disease patients

Abstract

Lexical and pictorial priming were examined in patients with Alzheimer's disease and in demented and nondemented patients with Parkinson's disease. Control subjects were divided into young and elderly. Lexical priming used a word‐stem completion task. Pictorial priming task was based on Rey's superimposed pictures test. Elderly normal subjects demonstrated lower lexical priming scores than those of young subjects. Analysis of covariance with age and educational level as covariates showed that normal controls, demented and nondemented Parkinsonian patients, and Alzheimer patients did not differ significantly on the lexical priming task. Pictorial priming scores did not differ significantly between elderly and younger controls. In contrast there was a striking impairment of pictorial priming in Parkinsonian patients, both demented and nondemented. Performance of subjects with mild Alzheimer's disease was superior to that of nondemented Parkinsonian patients. Our results suggest that performance in lexical priming task diminishes with physiological ageing but is unaffected by mild or moderate Alzheimer's disease. Our study also observes the existence of a selective pictorial priming deficit in Parkinson's disease; however, this deficit is not specific, as it is also observed to a lesser degree in Alzheimer's disease. It may therefore be concluded that the systems serving pictorial priming are both cortical and subcortical.