ASPECTS OF SPEECH PRODUCTION AND SPEECH COMPREHENSION IN HEBREW AGRAMMATISM OF SPEECH: TWO CASE STUDIES

The present study investigates the possible underlying causes for the constellation of deficits related to agrammatism of speech in Broca's aphasia. A case study approach is used so that an extensive and varied data base may be collected from performance on a multiplicity of tasks.

The first part of the dissertation compares two patients and two matched controls on various speech and language parameters from corpora of connected speech. Both patients indicate substantial intra- and inter-individual variability with respect to various manifestations of agrammatic language breakdown at both the morpheme and sentence level. These cannot be uniquely relegated to a deficit in syntax, the common view of agrammatism. The hypothesis is forwarded that a limitation in the operation of a speech output buffer has more explanatory power for the data at hand. This working hypothesis serves as a heuristic to predict a multi-directional dissociation across production and comprehension of various parts of speech.

In the second part of the dissertation, the patients' comprehension of prepositions, pronouns, and verbs is examined. The expected dissociation between comprehension and production of these parts of speech is upheld, in view of which further investigation is carried out on the patients' comprehension abilities at the sentence level. It is found that the patients' ability to comprehend various syntactic structures varies with task demands: Comprehension of passives and relative clauses in a picture pointing task manifests in the reported "asyntactic" impairment, whereas comprehension of the same structures in a less demanding picture verification task is greatly enhanced. When syntactic abilities are investigated in a grammaticality judgement task, the patients approach standard performance.

The third part of the dissertation reviews the relation between short term memory (STM) and comprehension deficits in the aphasiological literature. Preliminary testing is carried out of the hypothesis that STM deficits are causal in the constellation of impairments in agrammatism. Both patients are tested on tasks implicating various STM processes and are found to be differently deficited in relation to whether auditory or articulatory task components are employed. The relation between these deficited task components and speech production and comprehension abilities is discussed in view of neuroanatomical data based on the patients' CT scans.