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Cette thèse se propose de spécifier la relation entre les structures motrices et celles du langage en tant que systèmes coopératifs dans la construction du sens. Bien qu'un grand nombre d'études aient mis en évidence que les structures motrices sont impliquées dans le traitement du langage, il est encore difficile de déterminer le rôle de ces structures dans la compréhension. Les théories dites «incarnées» et «désincarnées» débattent de la nature de la représentation du sens des mots en termes de la nécessité des structures motrices pour le langage, en négligeant le fait que les conditions de leur activation n’ont pas été décrites. Des recherches récentes soulignent l’importance de la prise en compte des contextes dans lesquels le langage recrute l'activité motrice. Néanmoins, cette tendance est en contradiction avec les présomptions implicites dans la recherche sur l’interaction langage-motricité, qui se basent sur le modèle «deux-étapes» du traitement sémantique et sur la perspective du «dictionnaire» de la représentation du sens lexical. Dans ce cadre, le traitement du sens des mots est pris comme un processus modulaire. Ce n'est qu'une fois ce processus accompli que le contexte peut influencer la signification. Ces présomptions ont biaisé le débat sur le rôle de l'activité motrice induite par le langage, qui se réduirait à la question de savoir si l'activation motrice doit être considérée comme faisant partie de l'accès lexico-sémantique ou comme résultat de la construction d’un modèle de situation. Or, un grand nombre de travaux ont mis en évidence que le traitement lexico-sémantique et le contexte sont interdépendants. Cette connaissance provenant de la psycholinguistique doit être explicitement intégrée à la recherche sur le rôle de l'activité motrice induite par le langage. Dans un effort pour porter le débat hors de la discussion «lexical vs. post-lexical», cette thèse vise à déterminer les conditions sous lesquelles les contextes linguistiques déclenchent l'activité motrice. Pour ce faire, nous avons testé un nouvel outil qui analyse en ligne les modulations de la force de préhension pendant que les participants écoutaient des mots cibles intégrés dans différents contextes. Nos résultats montrent que quand le mot cible était un verbe d'action de la main et que la phrase focalisait l'action (« John signe le contrat»), une augmentation de la force de préhension était observée dans la fenêtre temporelle associée à la récupération lexico-sémantique. Aucune augmentation de la force de préhension comparable n’a été détectée lorsque le même mot d'action était intégré dans des phrases négatives («John ne signe pas le contrat») ou dans des phrases dont le focus avait été déplacé vers l'état mental de l'agent («John veut signer le contrat») ... / The present dissertation was conducted in order to specify the relationship between motor and language structures as cooperative systems in lexical meaning construction. Specifically, this thesis aimed at deepening our understanding of how the linguistic context coordinates the recruitment of motor structures during lexical semantic processing. Although the involvement of motor activity in action-related language comprehension is now sufficiently documented, the specific role that motor structures play in action language processing is still unclear. “Embodied” and “disembodied” theories debate the nature of meaning representation in terms of the necessity of motor structures, neglecting the fact that the conditions of their activation during language processing are not well-described. Very recent research has begun to note the necessity of exploring the context under which words trigger modality-specific cortical activity. However, this trend is at odds with implicit theoretical assumptions that have been made in research on motor-language crosstalk, which are based on the “two-step” model of semantic processing and the “dictionary-like” view of lexical meaning representation. Within such framework, word meaning recognition is taken to proceed in a modular fashion. Only after this process has concluded is the context thought to exert its effects. These assumptions have biased the debate on the role of language induced motor activity. The discussion has been centered on whether motor activation should be considered an integral part of the lexical access process or taken as the result of an ensuing “higher order” operation (i.e., situation model construction). A large body of work evidences that lexical semantic processing and semantic context are far more integrated and interdependent. It seems crucial to integrate this knowledge gained from psycholinguistics into the research on the role of language induced motor activity. In an effort to liberate the debate from the “lexical vs. post-lexical” discussion, this thesis aimed at determining the conditions under which language triggers motor activity. To accomplish these objectives, we introduced a novel tool that analyzes on-line modulations of grip-force while participants listened to specific target words embedded within different types of contexts. Our results show that when the target word was a hand action verb and the sentence focus centered on that action (“John signs the contract”), an increase of grip force was observed in the temporal window classically associated with lexical semantic processing. No comparable increase in grip force was detected when the same action word was embedded in negative sentences (“John doesn’t sign the contract”) or in sentences which focus was shifted towards the agent’s mental state (“John wants to sign the contract”). Our results suggest that the presence of an action word in an ...

Il razionale di questo progetto affonda le sue radici nelle recenti teorie che considerano il linguaggio come fondato sull’azione, e quindi strettamente collegato al sistema motorio. Negli ultimi decenni, infatti, la scoperta dei neuroni specchio, prima nella scimmia e poi negli esseri umani, ha portato ad un filone di ricerca spesso denominato “embodied language”. Grazie alle metodiche messe a disposizione dalle neuroscienze, ad oggi sono stati raccolti molti dati sperimentali a favore del legame tra sistema motorio e linguaggio, anche se la natura di questo legame non è del tutto chiara. In questa prospettiva, in aggiunta ai tradizionali strumenti di indagine come la Risonanza Magnetica Funzionale (fMRI) o la Stimolazione Magnetica Transcranica (TMS), anche la Realtà Virtuale (RV), che consente di provare un’”esperienza incorporata”, sembra possa aiutare i ricercatori a far luce sulle questioni ancora aperte. Il presente progetto, quindi, si compone di tre ricerche distinte, ciascuna delle quali pone ad oggetto di indagine una sfaccettatura diversa del complesso fenomeno dell’embodied language. Il primo esperimento è finalizzato ad indagare il ruolo della corteccia motoria primaria nei compiti di comprensione, utilizzando la rTMS; nel secondo esperimento viene introdotta la realtà virtuale per valutare se e come un’azione virtuale, grazie a un processo di simulazione, modula la comprensione di verbi; il terzo studio, infine, usando lo stesso ambiente virtuale del secondo studio, si propone di indagare il ruolo dell’azione virtuale durante l’apprendimento di una lingua straniera. / The rational of this project is rooted in the recent theories that consider language as grounded in action, and thus tightly tied to the motor system. In the last decades, the discovery of the mirror neurons in monkeys, and of the correspondent mirror neuron system in humans, led to a new research topic often called “embodied language”. Thanks to the methodics supplied by neuroscience, nowadays a great corpus of experimental data has been collected that support the link between language and motor system, even if the nature of this link is still not completely understood. In this perspective, beyond traditional tools such as Functional Magnetic Resonance (fMRI) or Transcranial Magnetic Stimulation (TMS), also Virtual reality (RV), which allows to create an embodied experience, seems suitable to shed light on the open questions. The present project, thereby, is structured in three independent researches, each one aiming at investigating one specific facet of the complex phenomenon of embodied language. The first experiment is designed to investigate the role of the primary motor cortex during language comprehension, using rTMS; in the second one, the virtual reality is introduced, in order to test if and how a virtual action, thanks to simulation, modulates verbs comprehension; the third study, finally, using the same virtual environment, aims at examining the role of the virtual action during foreign language learning.