Classification learning in Alzheimer's disease

Previous research has demonstrated that explicit recognition of dot patterns is impaired in amnesic patients with damage to the limbic-diencephalic memory system, while implicit categorization of the same kind of stimuli is preserved. The aim of the present study was to investigate the relationship between recognition and categorization performances in patients with Alzheimer's disease. Consistent with the findings in amnesic subjects, our results revealed that the explicit recognition of dot patterns was significantly impaired in Alzheimer's disease. However, implicit categorization functions were also disrupted. This was selective for the prototype stimuli; the categorization of non-prototype dot patterns was spared. The impaired category learning is likely to reflect the damage of modality-specific neocortical areas in Alzheimer's disease.