The Role of Agentive and Physical Forces in the Neural Representation of Motion Events

How does the brain represent information about motion events in relation to agentive and physical forces? In this study, we investigated the neural activity patterns associated with observing animated actions of agents (e.g., an agent hitting a chair) in comparison to similar movements of inanimate objects that were either shaped solely by the physics of the scene (e.g., gravity causing an object to fall down a hill and hit a chair) or initiated by agents (e.g., a visible agent causing an object to hit a chair). Using fMRI-based multivariate pattern analysis, this design allowed testing where in the brain the neural activity patterns associated with motion events change as a function of, or are invariant to, agentive versus physical forces behind them. Twenty-nine human participants (nine male) participated in the study. Cross-decoding revealed a shared neural representation of animate and inanimate motion events that is invariant to agentive or physical forces in regions spanning frontoparietal and posterior temporal cortices. In contrast, the right lateral occipitotemporal cortex showed higher sensitivity to agentive events, while the left dorsal premotor cortex was more sensitive to information about inanimate object events that were solely shaped by the physics of the scene.Significance Statement The brain's ability to interpret dynamic scenes is fundamental to our daily lives. In various frontoparietal and posterior temporal brain regions associated with human action understanding, our study reveals a common neural representation for animate and inanimate motion that is invariant to agentive or physical forces. By comparing events that vary in agentive or physical event dynamics, we also find that the right lateral occipitotemporal cortex and posterior superior temporal sulcus are more sensitive to animate agency, while the left dorsal premotor cortex and superior parietal lobules are more attuned to physical event dynamics. Our findings provide new insights, emphasizing the importance of an integrative approach that considers both agentive and physical aspects of motion events.