Category-specific naming deficit in Alzheimer's disease: the effect of a display by domain interaction

A category-specific naming effect penalizing living things has often been reported in patients suffering from Alzheimer's disease (AD) and in other brain damaged populations, while the opposite dissociation (i.e., lower accuracy in naming nonliving than living things) is much rarer. In this study, we investigated whether the use of line drawings (rather than color photographs) in picture-naming tasks could be a relevant factor in the emergence of a category effect penalizing living things and found evidence in favor of this hypothesis. We administered the same naming tasks comprising living and nonliving items to 10 subjects suffering from AD and 10 normal controls. Once the stimuli were line drawings and once color photographs. A reliable Group x Semantic domain interaction, indicating a disproportionate impairment for living things in the AD group, was only found when line drawings were presented. Results are discussed with reference to two competing approaches to category-specificity in brain damaged people. One assumes that category effects are due to the differential involvement of dedicated neural subsystems, the other emphasizes the role of cross domains imbalances in processing demands. We conclude that our findings lead support to the latter approach.