Does listening to action-related sentences modulate the activity of the motor system? Replication of a combined TMS and behavioral study.

Claudia Gianelli,Riccardo Dalla Volta

doi:10.3389/fpsyg.2014.01511

Abstract

The neurophysiological and behavioral correlates of action-related language processing have been debated for long time. A precursor in this field was the study by Buccino et al. (2005) combining transcranial magnetic stimulation (TMS) and behavioral measures (reaction times, RTs) to study the effect of listening to hand- and foot-related sentences. In the TMS experiment, the authors showed a decrease of motor evoked potentials (MEPs) recorded from hand muscles when processing hand-related verbs as compared to foot-related verbs. Similarly, MEPs recorded from leg muscles decreased when participants processed foot-related as compared to hand-related verbs. In the behavioral experiment, using the same stimuli and a semantic decision task the authors found slower RTs when the participants used the body effector (hand or foot) involved in the actual execution of the action expressed by the presented verb to give their motor responses. These findings were interpreted as an interference effect due to a simultaneous involvement of the motor system in both a language and a motor task. Our replication aimed to enlarge the sample size and replicate the findings with higher statistical power. The TMS experiment showed a significant modulation of hand MEPs, but in the sense of a motor facilitation when processing hand-related verbs. On the contrary, the behavioral experiment did not show significant results. The results are discussed within the general debate on the time-course of the modulation of motor cortex during implicit and explicit language processing and in relation to the studies on action observation/understanding.

Highlights

The target of this replication study is a seminal paper in the field of embodied language processing published by Buccino et al (2005) that combined TMS and behavioral techniques
A similar outcome would support the idea that a facilitation effect accompanies motor resonance during verb processing to what happens during action observation, questioning the hypothesis that when the motor system is engaged in both a linguistic and a motor task, participants pay a cost
Finding an interference effect would support the interpretation according to which this effect stems out when the motor system is activated for both understanding action sentences and planning motor responses, paying a cost in terms of RTs

Summary

Introduction

The target of this replication study is a seminal paper in the field of embodied language processing published by Buccino et al (2005) that combined TMS and behavioral techniques. In the behavioral experiment, using the same stimuli and a semantic decision task, the authors showed a similar interference effect, namely slower RTs when the participants’ body effector used to give the motor response corresponded to that involved in the execution of the action expressed by the presented verb. The authors claimed that a specific modulation of hand and foot/leg motor representations is crucially involved in processing language related to the corresponding effectors. These results were further confirmed by other studies (Boulenger et al, 2006; Sato et al, 2008; Dalla Volta et al, 2009; Gough et al, 2013; Marino et al, 2013)

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