Speech production in Broca’s agrammatic aphasia: Syntactic Tree Pruning

Broca’s agrammatic aphasia entails a syntactic deficit both in sentence comprehension and in sentence production. This chapter describes the intriguing pattern of deficits in speech production, and shows that this type of inquiry interacts with linguistic theory as well as with knowledge about brain-language relations. The syntactic tree, a syntactic construct that has originally been suggested based on purely linguistic grounds, is shown to be a useful tool to describe the deficit in production in agrammatism, and the role of the impaired brain area in syntactic production. The general idea is that the selective pattern of impairment in Broca’s agrammatic aphasia and the dissociations witnessed within and between languages follow from the inaccessibility of high nodes of the syntactic tree to agrammatic speakers. This causes syntactic structures that relate to high nodes of the tree to be impaired in agrammatism, whereas lower structures are unimpaired. The relative order of various syntactic abilities on the tree can also serve to explain degrees of agrammatic severity, as well as the path of spontaneous recovery from agrammatism.