Distinct profiles of temporal and frontoparietal cortex in representing actions across vision and language

Abstract

We understand actions from both observation and written text, pointing to a common neural representation of action concepts. However, which parts of the brain encode action concepts independently of stimulus type, say language or visual observation, is an unresolved question in neuroscience. An overlap of activation for action observation and sentence comprehension has been observed in frontoparietal and occipitotemporal cortex, but it is unclear whether this overlap points to the access of stimulus-general action concepts or result from functionally independent neural populations that are activated via one stimulus type but not the other. Using fMRI-based MVPA we found that frontoparietal areas encode representations of observed actions and corresponding written sentences in an overlapping way, but these representations did not generalize across stimulus type. By contrast, only left lateral posterior temporal cortex (LPTC) encoded action representations that generalize across observed action scenes and sentences. This observed stimulus generality was not modulated by verbalization or visual imagery. The representational organization of stimulus-general action information in LPTC could be predicted from models that describe basic agent-patient relations (object-and person-directedness) and the general semantic similarity between actions. Person-and object-directedness were topographically organized along a gradient in temporal cortex reminiscent of more posterior object distinctions, pointing to an overarching organizational principle of action and object knowledge in temporal and occipital cortex. Together, our findings revealed fundamentally distinct generalization profiles of temporal and frontoparietal cortex and suggest that LPTC represents aspects of action concepts by integrating more basic precursors in posterior cortex. ___________________________________________________________________________