Effects of the organization of practice on a mirror reading paradigm in Alzheimer’s Disease

Overview and aims: The contextual interference effect (CIE) – i.e., the advantage of a “random” over a “blocked” practice condition – has been shown in many studies on motor skill learning. In healthy populations, a random condition has a beneficial effect on transfer because it requires more cognitive investment, leading to more elaborated encoding.
The aim of this study was to investigate the CIE in Alzheimer’s patients with a perceptual skill learning task: the mirror-reading paradigm.
Methods: At each trial, 24 patients and 24 matched healthy subjects read pseudo-words presented as in a mirror. The blocked practice consisted in presenting pseudowords constructed with a subset of letters (set A), and then presenting pseudowords constructed with another subset (set B); in the random schedule, pseudo-words were constructed with letters belonging to both sets A and B. Transfer trials consisted of pseudowords built with new unlearned letters (set C).
Results: Results show that, in the transfer block following the learning phase, the blocked group read in the mirror significantly faster than the random group, whose performance did not improve; moreover, only the random practice was correlated with executive functioning.
Discussion and Conclusions: These results, which indicate that learning in AD is more efficient with a blocked schedule, are discussed in light of the current explanations of the CIE in both healthy subjects and AD patients.