Mental representations of action: the neural correlates of the verbal and motor components

Recent theories have hypothesized that semantic representations of action verbs and mental representations of action may be supported by partially overlapping, distributed brain networks. An fMRI experiment in healthy participants was designed to identify the common and specific regions in three different tasks from a common set of object drawings (manipulable man-made objects (MMO) and biological objects (MBO)): the generation of action words (GenA), the mental simulation of action (MSoA) and the mime of an action with the right hand (MimA). A fourth task, object naming (ON), was used as control for input/output effects. A null conjunction identified a common neural network consisting of nine regions distributed over premotor, parietal and occipital cortices. Within this common network, GenA elicited significantly more activation than either ON or MSoA in the left inferior frontal region, while MSoA elicited significantly more activation than either ON or GenA in the left superior parietal lobule. Both MSoA and GenA activated the left inferior parietal lobule more than ON. Furthermore, the left superior parietal cortex was activated to a greater extent by MMO than by MBO regardless of the tasks. These results suggest that action-denoting verbs and motor representations of the same actions activate a common frontal-parietal network. The left inferior parietal cortex and the left superior parietal cortex are likely to be involved in the retrieval of spatial-temporal features of object manipulation; the former might relate to the grasping and manipulation of any object while the latter might be linked to specific object-related gestures.