Neural correlates of manual action language: Comparative review, ALE meta-analysis and ROI meta-analysis.

Despite decades of research, the nature of the involvement of the motor system in action language processing is still controversial, and little is known about how processing action language relates to observing, imaging and executing motor actions. This study combines a systematic review of the literature, an ALE meta-analysis and a region-of-interest (ROI) meta-analysis to provide the first complete (qualitative and quantitative) account of the motor-related functional network involved in action language processing in comparison to activation reported during motor observation, motor imagery and motor execution. The review of the literature revealed that the methodology of action language studies differed considerably from the methodology of other motor-related processes which may have contributed to blurring the interpretations over the years. The ALE and ROI meta-analyses showed that the functional network of action language was more similar to observation than imagery and finally execution, following a motor gradation. Overall, our results point towards a more cognitive, as opposed to purely motoric, involvement of the motor system during action language processing.