Skill Learning and Repetition Priming in Alzheimer’s Disease

Several studies have shown with the mirror reading paradigm that procedural learning and repetition priming might be preserved in the early stages of Alzheimer’s disease (Deweer et al., 1994). Repetition priming is demonstrated by the reading times improvement for repeated words, while procedural learning is demonstrated when this improvement is also observed for new words. Our hypothesis was that this improvement could be due to a repetition priming effect for the letters rather than to the learning of a mirror reading skill. Indeed, because the same letters are presented throughout the task, a repetition priming effect could be sufficient to explain the improvement of performance. In order to test this hypothesis, we have administered to 20 young and elderly subjects and to 20 Alzheimer’s patients a new mirror reading task including two phases: an acquisition phase comprising pseudo-words constructed with one part of the alphabet, and a test phase in which both pseudo-words constructed with the same part of the alphabet and pseudo-words constructed with another part of the alphabet were presented. Reading faster the new pseudo-words composed with the repeated letters would reflect a repetition priming effect, while reading faster pseudo-words composed with “new” letters would reflect a procedural learning effect. Results show comparable repetition priming effects in Alzheimer’s patients and in young and elderly subjects, whereas only young and elderly subjects showed a procedural learning effect. These results suggest, contrary to previous studies, that the learning of a new perceptual skill could be not preserved in Alzheimer’s disease.