Dissociations among functional categories in Korean agrammatism.

This study investigated the hypothesis that the syntactic trees formed by individuals with agrammatic aphasia cannot be constructed any higher than an impaired node as suggested by the tree-pruning hypothesis (Friedman, 1994; Friedmann & Grodzinsky, 1997) and hypothesis. It also examined their following implication that the members of a certain functional category are subject to the same degree of impairment. Two experiments were conducted to investigate a Korean agrammatic patient's use and understanding of three functional categories--Mood, Tense, and Complementizer. The results showed a dissociation among functional categories that preserves the higher node while leaving the lower node impaired both in production and comprehension. Another dissociation was found among members of the same category depending on their linear position in the clause. These results contrast with the predictions of the tree-pruning hypothesis, suggesting that the nearer to the end of the clause a functional element is located, the better it is preserved in Korean agrammatism. Copyright 2002 Elsevier Science (USA)