How specifically are action verbs represented in the neural motor system: an fMRI study

Embodied accounts of language processing suggest that sensorimotor areas, generally dedicated to perception and action, are also involved in the processing and representation of word meaning. Support for such accounts comes from studies showing that language about actions selectively modulates the execution of congruent and incongruent motor responses (e.g., Glenberg & Kaschak, 2002), and from functional neuroimaging studies showing that understanding action-related language recruits sensorimotor brain areas (e.g. Hauk, Johnsrude, & Pulvermueller, 2004). In the current experiment we explored the basis of the neural motor system's involvement in representing words denoting actions. Specifically, we investigated whether the motor system's involvement is modulated by the specificity of the kinematics associated with a word. Previous research in the visual domain indicates that words denoting basic level category members lacking a specific form (e.g., bird) are less richly encoded within visual areas than words denoting subordinate level members (e.g., pelican), for which the visual form is better specified (Gauthier, Anderson, Tarr, Skudlarski, & Gore, 1997). In the present study we extend these findings to the motor domain. Modulation of the BOLD response elicited by verbs denoting a general motor program (e.g., to clean) was compared to modulation elicited by verbs denoting a more specific motor program (e.g., to wipe). Conform with our hypothesis, a region within the bilateral inferior parietal lobule, typically serving the representation of action plans and goals, was sensitive to the specificity of motor programs associated with the action verbs. These findings contribute to the growing body of research on embodied language representations by showing that the concreteness of an action-semantic feature is reflected in the neural response to action verbs.