Mirror reading in Alzheimer's disease: normal skill learning and acquisition of item-specific information

Alzheimer's disease (AD) is characterized by severe explicit memory deficits and sparing of procedural learning. Most studies of skill learning in AD have been restricted to motor skills. This experiment was aimed at extending these studies to the domain of perceptual-verbal skills. Thirteen AD patients and 9 normal elderly controls were administered several explicit memory tests and a mirror reading paradigm with both unique and repeated word triads. In this last task, AD patients showed normal learning for unique word triads, that is, normal acquisition of the skill. Moreover, they benefitted from repeated triads to the same extent as did normal controls, although they were impaired in discriminating these repeated words from distractors at later recognition. These data demonstrate that patients with AD: (a) are able to learn and retain a perceptual-verbal skill at a normal rate; (b) can learn item-specific information (repeated triads) at a normal rate, even though their explicit memory is severely impaired. It is hypothesized that learning of item-specific information relies on repetition priming effects rather than on explicit memory processes.