Dissociations among structural-perceptual, lexical-semantic, and event-fact memory systems in Alzheimer, amnesic, and normal subjects.

Patients with Alzheimer's disease (AD), patients with global amnesia (AMN), and normal control (NC) subjects received tests of recall and recognition, word-completion priming, and incomplete-picture priming. The AD and AMN patients had impaired recall and recognition. The AD patients, but not the AMN patients, had impaired word-completion priming. In contrast, the AD patients had intact incomplete-picture priming, a form of priming shown to be perceptual in normal subjects. These results provide neuropsychological evidence for a dissociation between two components of repetition priming, perceptual priming as measured with identification tasks and nonperceptual priming as measured with generation tasks. Preserved perceptual priming in AD may be mediated by the occipital regions that are relatively spared in AD; compromised nonperceptual priming may be mediated by temporal regions that show dense neuropathological changes early in AD.