Understanding of relational time terms before and after in Parkinsonian patients.

The role of the relational time terms before and after in language comprehension was investigated using patients with Parkinson's disease (PD) and normal controls (NC) in Greek. Results lead to the following four conclusions: (a) Comprehension by PD patients of before and after constructions displaying syntactic, semantic, and cognitive constraints equivalent to those of English is significantly different from that of NC matched on chronological age, sex, education, and socioeconomic status. (b) Before is better understood than after. (c) Syntactic variables, when semantic effects are partialed out, do not affect performance. The same is true of semantic effects when syntactic variables are partialed out. (d) Order of mention of events is a predominant source of errors when syntax and semantics are controlled. The data are discussed in relation both to findings with aphasics and to developmental results on the same time terms.