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Communication Dans Un Congrès Année : 2010

Sentence processing in the left ventral premotor cortex: rTMS evidence

Résumé

Understanding action-related language might require some motor simulation of the action being described. Consistent with this idea, a number of functional imaging studies have shown activation in motor and premotor areas during language tasks such as passively attending to action words and phrases. In a recent fMRI study, we also showed robust activation in the superior part of the left ventral premotor cortex (svPMC) during sentence listening, but also during sentence repetition and sentence generation, demonstrating that the left svPMC is a core region for sentence processing. Moreover, our results showed that activation in svPMC was modulated by semantic content (action, object), suggesting a role for this region in sentence processing at a semantic level. The goal of this study was to examine the importance of svPMC during sentence processing using 1 Hz low-frequency repetitive TMS (rTMS). To this aim, 15 right-handed students from The University of Chicago were recruited. The experiment consisted of two rTMS and sham sessions, which were separated by 1 hour and fully counterbalanced across participants. The svPMC stimulation site was located with frameless stereotaxy at the beginning of each session on the basis of each participant's anatomical MRI scan. In both sessions, the TMS coil was positioned over the left svPMC using the same localization procedure. In the TMS session, 900 pulses were applied at a frequency of 1 Hz, with stimulation intensity at 110% of individual resting motor threshold. The sham stimulation was performed by presenting participants with recorded TMS noise mimicking actual stimulation. Participants underwent two identical experimental sessions following rTMS and sham stimulation. On each trial, a short concrete sentence was presented, which was followed by a target word that was either semantically related to the sentence or not (e.g., "The hammer is rusty"/"Nail"). Participants were asked to decide whether the target word was semantically related to the sentence by pressing one of two buttons. The sentences described either manual actions, manipulable objects, non-manipulable objects or orofacial actions. A three-way repeated-measures ANOVA was performed with TMS (stimulation, sham), Semantics (manual actions, manipulable objects, non-manipulable objects or orofacial actions) and Priming (related, unrelated) as the within-subject factors and reaction-timed (RT) as the dependent variable. Results revealed a strong 2-way interaction between TMS and priming (p = 0.00001). While after sham session, the experimental manipulation resulted in a classic priming effect (facilitation), with related trials being processed more quickly than unrelated trials, no such priming occurred after TMS stimulation. Furthermore, a 3-way interaction demonstrated this effect to be maximal for the manual action sentences. These results confirm that the left sPMv is involved in processing sentences and, consistent with a functional role for the motor system in language comprehension, demonstrate that this region is sensitive to their semantic content. Interestingly, our previous fMRI results failed to show activation of svPMC during action observation, which suggest that the process by which action observation and action sentences are understood do not necessarily imply the same motor regions.
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Dates et versions

hal-00516769 , version 1 (11-09-2010)

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  • HAL Id : hal-00516769 , version 1

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Pascale Tremblay, Marc Sato, Steve Small. Sentence processing in the left ventral premotor cortex: rTMS evidence. NLC 2010 - 2nd Annual Neurobiology of Language Conference, Nov 2010, San Diego, Californie, United States. ⟨hal-00516769⟩
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