Neuropragmatic Speech-Language Deficits Specific To Speech Act Type Following Left-Hemispheric Lesion

Introduction: Aphasia and other language deficits are frequently seen as structural-linguistic impairments affecting speech sounds, vocabulary and syntax. In contrast, pragmatic-linguistic functions such as the ability to use linguistic materials in order to perform linguistic actions, i.e. speech acts, are attributed to the right, non-dominant hemisphere. However, anecdotal reports have long suggested that the ability to use and understand a linguistic form may strongly depend on context and communicative purpose, as, for example, in Baillarger’s case of a woman who could not ‘name’ her daughter but had no problem to express her regret by saying: ‘My dear little Jacqueline, I even don’t know your name anymore.’ Methods: We tested 30 patients with post-stroke aphasia due to leftperisylvian lesions using a new test (Action Communication Test, ACT), which contrasts the abilities to use words and phrases for confrontation naming of objects and for requesting objects from a partner. Word and picture materials were matched for physical, psycholinguistic and psychological features between naming and requesting conditions and counterbalanced across subjects. Results: 17 patients tended to perform better for one of the speech act types compared with the other. 7 patients showed pronounced and significant performance differences between speech act categories (3 naming > requesting; 4 requesting > naming). The double dissociation between assertive naming and directive requesting was unrelated to target objects, linguistic materials or socioeconomic features of the patients. Lesion maps showed overall larger lesions in the patients with predominant naming deficit compared with the request-focused group, but no clear anatomical dissociation. Conclusions: Embedding of language structures in action and communicative interaction contexts significantly influence language performance in a subset of aphasic patients. The observed double dissociation in the ability to perform assertive (naming) and directive speech acts (requesting) calls for a revision of current concepts of aphasia as a structural deficit. The speech-act specific impairments make it evident that linguistic-pragmatic analysis of lefthemispheric language deficits is important for obtaining a more complete picture of the nature of aphasia and for improved planning of therapy of speech, language and communication.