German Broca’s and Wernicke’s aphasics display similar deficits in syntactic performance / Eva Wimmer

German Broca’s and Wernicke’s aphasics display similar deficits in syntactic performance / Eva Wimmer. In "Perspectives neuropsycholinguistiques sur l'aphasie - NeuroPsychoLinguistic Perspectives on Aphasia", colloque international organisé par l'Unité de Recherche Interdisciplinaire Octogone de l'Université Toulouse II-Le Mirail (France). Toulouse, 21-23 juin 2012.

With respect to syntactic disorders in aphasia, research primarily focuses on non-fluent agrammatic Broca’s aphasia, for which specific deficits in morphology and syntax have been observed in language production and comprehension (cf. Grodzinsky 2000) while the lexicon is considered as relatively intact. In contrast, less attention has been given to the fluent speech of Wernicke’s aphasia. Due to their lexical retrieval problems and so-called paragrammatic speech style entailing many semantic and phonological paraphasias, this type of aphasia is considered by many as the mirror image of Broca’s aphasia i.e. a lexical disorder sparing syntax. However, some studies have found evidence for impaired syntactic structures in the spontaneous speech of Wernicke’s aphasics and recent comprehension studies show similar syntactic comprehension patterns of Broca’s and Wernicke’s aphasics (cf. Edwards 2005). The aim of our study is therefore to provide new data by investigating the syntactic abilities of German Wernicke’s aphasics and to find out if there are differences to the syntactic performance of German Broca’s subjects with respect to the very same structured tasks.The participants of this study were nine German Wernicke’s aphasics with typical paragrammatic speech, a group of nine agrammatic Broca’s aphasics investigated previously (Neuhaus & Penke 2008) and ten unimpaired age-matched subjects. Patients were diagnosed and classified on the basis of the Aachen-Aphasia-Test battery.
The tasks were the following:
- Verb placement task: completion of 20 main clauses and 10 subordinate clauses with a given simplex verb form.
- Elicitation and repetition of wh-subject, wh-object and wh-adjunct-questions (n = 54 in elicitation, n = 30 in repetition), e.g: Wer füttert den Jungen ? (,Who feeds the boy?’)
- Comprehension of who or which-subject-and -object-questions (picture pointing task with3-person-scenarios, n = 60), e.g.: Welchen Mann bürstet die Frau? (,Which man is the woman brushing?’).

The results of the verb placement test indicate that verb placement patterns in main and subordinate clauses are generally preserved in Wernicke’s aphasia (91% correct) as well as in Broca’s aphasia (89%). In contrast, both Broca’s and Wernicke’s subjects have difficulties in producing and understanding wh-questions. With respect to production, Wernicke’s aphasics show weaker overall results (elicitation: 47% correct,repetition: 59%) than Broca‘s aphasics (elicitation: 66%, repetition: 81%) while comprehensionscores are more similar (Wernicke: 44% correct, Broca: 54%). In production as well as comprehension Wernicke’s subjects display performance patterns which are similar to Broca’s subjects, i.e.wh-object-questions are more error prone than wh-subject-questions, and the error patterns in production are also comparable (e.g. substitutions of wh-object questions by wh-subject questions).

In sum, we find that contrary to the traditional picture of a double-dissociation between syntax and lexicon in Broca’s and Wernicke’s aphasia, not only Broca’s aphasics, but alsoWernicke’s aphasics display specific problems with complex syntactic structures like wh-questions.Group differences such as the greater variability in Wernicke’s subjects might result from their greater lexical/semantic deficit. We will argue that the results of both groups are best explained by a processing deficit. Under such an approach (cf. e.g. Kolk &Heeschen 1992), aphasic performance varies according to the amount of processing costs which are highly dependent not only on structural complexity, but also on factors such as task demands and individual processing capacity.