Neuronale Korrelate lexikalischen Suchverhaltens in der aphasischen Spontansprache: Ein Einzelfall

The neural correlates of agrammatism: Evidence from aphasic and healthy speakers performing an overt picture description task

Functional brain imaging studies have improved our knowledge of the neural localization of language functions and the functional reorganization after a lesion. However, the neural correlates of agrammatic symptoms in aphasia remain largely unknown. The present fMRI study examined the neural correlates of morpho-syntactic encoding and agrammatic errors in continuous language production by combining three approaches. First, the neural mechanisms underlying natural morpho-syntactic processing in a picture description task were analyzed in 15 healthy speakers. Second, agrammatic-like speech behavior was induced in the same group of healthy speakers to study the underlying functional processes by limiting the utterance length. In a third approach, five agrammatic participants performed the picture description task to gain insights in the neural correlates of agrammatism and the functional reorganization of language processing after stroke. In all approaches, utterances were analyzed for syntactic completeness, complexity, and morphology. Event-related data analysis was conducted by defining every clause-like unit (CLU) as an event with its onset-time and duration. Agrammatic and correct CLUs were contrasted. Due to the small sample size as well as heterogeneous lesion sizes and sites with lesion foci in the insula lobe, inferior frontal, superior temporal and inferior parietal areas the activation patterns in the agrammatic speakers were analyzed on a single subject level. In the group of healthy speakers, posterior temporal and inferior parietal areas were associated with greater morpho-syntactic demands in complete and complex CLUs. The intentional manipulation of morpho-syntactic structures and the omission of function words were associated with additional inferior frontal activation. Overall, the results revealed that the investigation of the neural correlates of agrammatic language production can be reasonably conducted with an overt language production paradigm.

Taboo: a novel paradigm to elicit aphasia-like trouble-indicating behaviour in normally speaking individuals

Two important research lines in neuro- and psycholinguistics are studying natural or experimentally induced slips of the tongue and investigating the symptom patterns of aphasic individuals. Only few studies have focused on explaining aphasic symptoms by provoking aphasic symptoms in healthy speakers. While all experimental techniques have so far dealt with the single word or the sentence level, the current study intended to provoke aphasia-like trouble-indicating behaviour (i.e. prepairs and repairs) in the spontaneous language production of unimpaired speakers. In their descriptions of complex pictures, the participants were requested to avoid particular words terming central elements of the pictures. The results show that the error pattern provoked by the novel "taboo" paradigm resembled substantially the pattern of aphasic individuals. Consequently, the paradigm is applicable for further studies, e.g. for bringing forward the understanding of spontaneous language production or for comparing the neurofunctional basis of errors in healthy and aphasic speakers.