Subjective understanding of actions and emotions involves the interplay of the semantic and action observation networks in the brain

Previous studies have investigated the neural basis of action and emotion perception conveyed by whole body postures and movements. However, subjective understanding of other peoples bodily actions and emotions, raises different issues that are currently not well understood and have so far seldom been investigated. In this 7T fMRI study, we proceeded beyond conventional univariate/multivariate analyses with predefined categories, and examined the representational geometry of subjective action- and emotion-understanding by mapping individual subjective reports with word embeddings. Dimensionality reduction revealed that the representations for perceived action and emotion were high dimensional, each correlated to but were not reducible to the predefined action and emotion categories. Searchlight representational similarity analysis showed that the representations in the left middle superior temporal sulcus and left dorsal premotor cortex corresponded to the subjective action and emotion understanding of the participants. Furthermore, using task-residual functional connectivity and hierarchical clustering, we found that areas in the action observation network and the semantic/default-mode network were functionally connected to these two seed regions, and showed similar representations. Our study provides direct evidence that both networks were concurrently involved in subjective action and emotion understanding. Our approach shows how subjective understanding of action and emotion stimuli can be reliably studied and complement insights based on from predefined stimulus categories.