Are semantic errors actually semantic?: Evidence from Alzheimer's disease

Patients with Alzheimer's disease (AD) produce a high rate of semantic erro rs when naming to confrontation. This is considered to be one of the many c onsequences of their semantic memory deficit. However, it has been shown, i n aphasic patients with focal lesions, that semantic errors could arise fro m impairment to any one of the levels in the naming process. To check this hypothesis in AD, we assessed in lj patients the capacity to name and acces s semantic knowledge (bp multiple-choice probe questions) about 14 objects presented successively in the visual, tactile, auditory, and verbal modalit ies. In the visual naming task, 33 ;errors were recorded: 26 (78.8%) were s emantic and 7 (21.2%) were unrelated errors. Of the 26 semantic errors, 8 w ere related to a deficit of the semantic knowledge related to the item and 17 to a deficit in the retrieval of the phonological form of the word. One was associated with a deficit of access to semantic knowledge in the visual modality. The 7 unrelated errors were associated with a loss of semantic k nowledge for 4 and deficit of access to the phonological form for 3. In con clusion, this study shows that semantic errors do not systematically reflec t a deficit of semantic knowledge in Alzheimer's disease. It also seems tha t unrelated errors are more frequently related to semantic deficits than se mantic errors in this population. (C) 2001 Academic Press.