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Neural resources shared by tool-use and language
Poster C61 in Poster Session C, Friday, October 7, 10:15 am - 12:00 pm EDT, Millennium Hall
Simon THIBAULT1,2, Véronique BOULENGER3, Alice ROY3, Claudio BROZZOLI1; 1Lyon Neuroscience Research Center - ImpAct Team - INSERM - CNRS - France, 2Moss Rehabilitation Research Institute - Thomas Jefferson University - USA, 3Language Dynamics - CNRS Lyon - France
Humans own strikingly developed communications abilities characterized by their language but also advanced motor skills as revealed by their skillful use of a large set of tools. According to longstanding evolutionary theories, language could have built on pre-existing motor functions leaving observable parallels between linguistic and motor domains in neural activity. In particular, left hemisphere regions such as the inferior frontal gyrus (IFG), supramarginal gyrus (SMG) and the occipito-temporal (OTC) cortex, as well as the basal ganglia (BG) have been suggested to support both tool use and language processes. In two fMRI experiments on healthy right-handed French native speakers (20-40 y-o), we studied the shared neural resources involved for both tool use and linguistic abilities, such as phonology, semantics and syntax. In the first experiment, 20 participants moved a peg with a 30-cm pliers and with the bare hand as control; the same participants also underwent a semantic and phonological task. The semantic task consisted in a lexical decision task with two semantic categories: tool and animal nouns. The phonological task consisted in an identification task of syllables (/ba/ and /da/ along a continuum). In the second experiment, across seven distinct runs, 40 naïve participants were assessed on their comprehension of complex relative clauses (subject and object relatives) and an adapted version of the motor task allowing to reliably measure the action execution time. In the first experiment, planning an action with a tool activated left hemisphere regions such as the IFG, SMG, OTC and the BG bilaterally. Using representational similarity analysis (RSA), we found that the neural activity elicited by tool and animal nouns was significantly decoded within the IFG and OTC recruited by tool use. No such effect was found when attempting to decode the neural activities elicited by the syllables. In the second experiment, we identified regions of interest jointly involved by the two relative clauses. The results showed within the left BG, a greater averaged signal for the object relatives in comparison to subject relatives, as well as for grasping a peg with a tool, while it was much lower for the bare hand. A similar trend was observed in the right BG. In the left BG, we considered the time course of the activations across the seven runs; and we found that the averaged correlation scores between object relatives and tool grasping was significant, suggesting a comparable decrease of the signal for each condition. No such relation was observed for the correlation scores between object relatives and hand grasping or between subject relatives and tool grasping. Overall, these results highlight the brain areas that are activated by both tool use and language. In particular, in the OTC, IFG and BG a co-localization was observed. The shared network might subserve similar functions for tool use and linguistic functions: semantics may support tool use and vice versa, while hierarchical processing may be crucial for both syntax and tool use. The characterization of these neural overlap may open new avenues for developing new cross-domain learning and rehabilitation strategies.
Topic Areas: Syntax, Meaning: Lexical Semantics