Models of actor-specific range of motion are encoded in the extrastriate body area

Models of actor-specific range of motion (or biomechanical limits) shapes perception and (inter)actions. This functional magnetic resonance imaging study tested the hypothesis that these models are encoded in the extrastriate body area. Participants were first introduced with the maximal amplitude of arm and leg movements of a "rigid" and a "flexible" actor. Then, we measured the blood oxygenation level dependent response in 25 participants while they watched video clips depicting these actors performing either "small" movements that were "possible" to perform for both actors, "large" ones that were "impossible" for both actors and "intermediate" ones that were possible only for the "flexible" actor. Results aligned with the 2 predictions of our hypothesis: (i) extrastriate body area responded more strongly to impossible than possible movements; (ii) extrastriate body area categorized intermediate movements as "possible" or "impossible" depending on each actor's specific range of motion. The results of additional analyses suggested that extrastriate body area encodes actor-specific range of motion at the level of specific body parts, and as a probability function. Finally, the results of whole brain and functional connectivity analyses suggested that the right posterior superior temporal sulcus may also play an important role in encoding information about actor-specific biomechanical limits.