THE ROLE OF SEMANTIC MEMORY IN OBJECT USE

Does semantic knowledge of objects mediate object selection and use? W e present data from two patients that speak to this question. The firs t, DM, is a semantic dementia patient previously reported by Breedin, Saffran, and Coslett (1994) who, despite moderate to severe loss of fu nctional and associative object knowledge, was nevertheless able to pe rform almost normally on single-object use and on more complex tests o f naturalistic action. The second, HE, is a dementia patient who exhib ited an executive disorder but performed as well as controls on a deta iled battery of semantic memory and single-object use tests. Unlike DM , he made numerous errors on the naturalistic action tests, among whic h were errors of object selection and usage. Taken together, these dat a suggest that intact semantic memory for objects is neither necessary nor sufficient to ensure good object utilisation in naturalistic acti on. The data cannot be accommodated by accounts postulating that actio n with objects is performed exclusively via nonsemantic or visual sema ntic routes, but are most consistent with an account in which nonseman tic information augments deficient functional/associational semantic e lements in an action-oriented network.