Different variables predict anomia in different subjects: a longitudinal study of two Alzheimer's patients.

Two Alzheimer's patients participated in a longitudinal study of picture naming aimed at analysing the effect of lexical frequency, age of acquisition, stimulus familiarity, word length, name imageability, visual complexity and semantic category membership on naming success. The results were analysed with a new method [Capitani, E., & Laiacona, M. (2004). A method for studying the evolution of naming error types in the recovery of acute aphasia: A single-patient and single-stimulus approach. Neuropsychologia, 42, 613-623] that allows us to consider the consistency of responses to stimuli over repeated testing within clinical stages. The experiment was carried out as a longitudinal study of single cases, and the effect of each variable was estimated after removing the overlap with the other predictors. The semantic category of stimuli was not an influential factor for either patient. Other findings sharply distinguished between the two patients. In one case, disease-related decline consistently affected mainly late acquired names, whereas in the other case the decline affected names corresponding to low-familiarity items. To interpret this contrast, we further analysed the quality of the errors produced by each patient. This study shows that the psycholinguistic characteristics of a stimulus may exert varying influence in different patients, warranting further development of this line of inquiry.