Degraded semantic knowledge and accurate object use.

In the present paper we report the performance on object use and on semantic tasks of two patients, D.L. with probable semantic dementia, and A.M. with an atypical onset of dementia of Alzheimer, assessed twice two years apart. In particular, we investigated whether the patients' ability to use objects degraded as a function of their semantic knowledge about those objects. Results from the two assessments in 2002 and in 2004 confirmed that both patients had a selective loss of the lexical-semantic knowledge, despite a relative preservation of the other cognitive abilities including object use. This pattern of results suggests that semantic knowledge is not necessarily involved in the correct use of objects.