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Co-Auteur(s): Barbara MOSER-MERCER Narly GOLESTANI

The neural basis of simultaneous interpretation: extreme language control is executive control

Abstract/Résumé: A common, yet substantial, challenge to speech production and perception is multilingualism, wherein an individual is proficient in more than one language. The multilingual brain is required to continuously select between languages for expression or comprehension. An increasing body of work indicates that this constant demand has profound cognitive consequences, manifest as a bilingual advantage on a range of non-linguistic tasks that tap executive processes. It has been suggested that the advantages observed stem from the need for the bilingual brain to frequently engage in inhibitory control, and an attendant practice-driven enhancement of the inhibitory network or of a more general “conflict monitoring system”. It appears that executive processes and multi-lingual language management depend upon similar, overlapping networks. In order to further elucidate the brain basis of language control, we examined simultaneous interpretation (SI), a task that places extreme demands on executive and linguistic control. SI requires the simultaneous management of speech comprehension and production while monitoring the accuracy of the interpretation. Successful SI depends not just upon mastery of the two languages involved, but also advanced management of cognitive resources. In order to determine the brain basis of SI, we compared the brain regions activated in a group of 52 non-expert multilingual individuals while listening to sentences, simultaneously repeating sentences and simultaneously interpreting sentences. Results show that SI depends upon interacting networks involved in articulation, speech comprehension, translation and executive processes. The data demonstrate that, in addition to speech perception and production networks, the process of SI recruits the basal ganglia, which are heavily implicated in cortico-subcortical executive control networks central to action-initiation, inhibition and response-conflict management. 22 of the participants participated in a 15-month SI training program. They were scanned again performing the same SI task. We found significant training-related decreases in brain activation during SI in left inferior frontal gyrus (associated with syntactic processing, verbal working memory, and cognitive control of semantic memory), caudate nucleus (involved in the cognitive control of action and associated with accessing cross-language lexical alternatives) and in left somato-motor cortex (involved in the processing of articulatory-motor feedback). These results suggest that SI-training induces functional changes characterized by more efficient neural processing in linguistic as well as in non-linguistic brain regions known to be involved in aspects of cognitive and executive control.