Role and time course of the modulation of the motor system during the processing of action-related verbs

Even though a growing body of research has shown that the processing of action language affects the planning and
execution of motor acts, several aspects of this interaction are still hotly debated. The directionality (i.e. does understanding
action-related language induce a facilitation or an interference with the corresponding action?), the time course, and the
nature of the interaction (i.e. under what conditions does the phenomenon occur?) are largely unclear. To further explore
this topic we exploited a go/no-go paradigm in which healthy participants were required to perform arm reaching
movements toward a target when verbs expressing either hand or foot actions were shown, and to refrain from moving
when abstract verbs were presented. We found that reaction times (RT) and percentages of errors increased when the verb
involved the same effector used to give the response. This interference occurred very early, when the interval between verb
presentation and the delivery of the go signal was 50 ms, and could be elicited until this delay was about 600 ms. In
addition, RTs were faster when subjects used the right arm than when they used the left arm, suggesting that action–verb
understanding is left-lateralized. Furthermore, when the color of the printed verb and not its meaning was the cue for
movement execution the differences between RTs and error percentages between verb categories disappeared,
unequivocally indicating that the phenomenon occurs only when the semantic content of a verb has to be retrieved. These
results are compatible with the theory of embodied language, which hypothesizes that comprehending verbal descriptions
of actions relies on an internal simulation of the sensory–motor experience of the action, and provide a new and detailed
view of the interplay between action language and motor acts