Abstract
Both temporal and frontoparietal brain areas are associated with the representation of knowledge about the world, in particular about actions. However, what these brain regions represent and precisely how they differ remains unknown. Here, we reveal distinct functional profiles of lateral temporal and frontoparietal cortex using fMRI-based MVPA. Frontoparietal areas encode representations of observed actions and corresponding written sentences in an overlapping way, but these representations do not generalize across stimulus type. By contrast, only left lateral posterior temporal cortex (LPTC) encodes action representations that generalize across observed action scenes and written descriptions. The representational organization of stimulus-general action information in LPTC can be predicted from models that describe basic agent-patient relations (object- and person-directedness) and the general semantic similarity between actions. Our results suggest that LPTC encodes general, conceptual aspects of actions whereas frontoparietal representations appear to be tied to specific stimulus types.
Highlights
Both temporal and frontoparietal brain areas are associated with the representation of knowledge about the world, in particular about actions
In two functional magnetic resonance imaging sessions, participants recognized actions presented in videos and corresponding visually presented sentences (Fig. 1)
This analysis identified a single cluster in the left lateral posterior temporal cortex (LPTC), peaking in posterior middle temporal gyrus (pMTG), and extending dorsally into posterior superior temporal sulcus and ventrally into inferior temporal gyrus (Fig. 2a, Table 1)
Summary
Both temporal and frontoparietal brain areas are associated with the representation of knowledge about the world, in particular about actions. Both areas are activated during the semantic processing of action words, which lack specific perceptual details of concrete action exemplars[15,16] These findings raise a puzzling question: if both posterior temporal and anterior parietal cortex are capable of representing actions at similar, high levels of generality, what are their different roles in recognition and memory? Neuroimaging studies revealed that understanding actions from observation and from written sentences activates overlapping brain networks in prefrontal and parietal cortex as well as in occipitotemporal brain areas, in posterior middle temporal gyrus (pMTG) and surrounding areas in lateral posterior temporal cortex (LPTC)[17,18,19] This overlap in activation is usually taken as evidence for the recruitment of the same neural representations accessed during both action observation and sentence comprehension, which would suggest that these representations encode action knowledge at stimulus-independent, conceptual levels. The findings suggest that LPTC encodes conceptual action information that can be accessed independently of stimulus type whereas frontoparietal areas represent action information in a stimulus type-specific manner
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