Picture naming and progression of Alzheimer's disease: an analysis of error types

Seven patients affected by Dementia of the Alzheimer Type (DAT) took part in a longitudinal study aimed at assessing the qualitative and quantitative evolution of picture naming impairment. The follow-up lasted 6-36 months and the patients were examined at intervals of 6 months or longer. We found that the absolute number of lexical-semantic errors tended to be constant or to rise slightly until an advanced stage of DAT severity was reached. However, the proportion of errors of the lexical-semantic type in relation to the overall number of errors showed a decline as the disease progressed, with empty and unrelated responses being increasingly observed. Visual errors were generally a minority; they were produced in different proportions for:ach patient but did not vary greatly over time. For the observed patients, the proportion of lexical and semantic errors was inversely related to the overall naming performance, following a negative logarithmic function.This finding was replicated analysing cross-sectional data from another 24 DAT patients who were given the same naming task. (C) 1998 Elsevier Science Ltd. All rights reserved.