Category specificity in an agrammatic patient: the relative impairment of verb retrieval and comprehension

We report our investigations of a severely agrammatic patient (ROX). A striking feature of ROX's spontaneous speech was his extremely abnormal verb phrase constructions. We established that ROX was impaired both in the retrieval and in the comprehension of action names and verbs which contrasted with his generally excellent comprehension and retrieval of nouns. First we describe his impaired performance on certain sentence comprehension tests. Secondly we document his deficits in naming common actions and our attempt to remedy his impairment. Thirdly we investigate his comprehension of semantically and thematically related nouns and verbs. ROX's agrammatism is discussed from the perspective of category specificity. It is argued that his semantic representation of verbs is impaired, and that this lexical deficit may well be at the core of this type of agrammatism.