Abstract
Object representations include knowledge of their shape, function, manipulability and use kinematics, organized in various dedicated neural networks. Here, we tested the role of motor-manipulation knowledge and experience on object perception in people born without hands (i.e., upper limb dysplasics) who, because of this deficit, cannot use certain tools for which they have intact knowledge otherwise. Recently, we have shown that these right-footed individuals have similar hand-tool association and intact action observation networks as compared to typically developed controls. Therefore, we anticipated representation of motor manipulation knowledge and experience to be evident in the left-lateralized praxis and tool-use network. Surprisingly, we found a result that is not interpretable in this classical framework. Specifically, presentation of manipulable objects with which the upper limb dysplasics had motor experience preferentially activated a widespread, right-lateralized network that included right ventral visual cortex, posterior middle temporal lobe, and middle frontal gyrus, not the left-lateralized, tool-selective network. However, object decoding based on the dysplasics’ motor knowledge highlighted classical tool and action/praxis regions bilaterally. While we are puzzled by these results, they possible suggest that praxis network lateralization is unique to hand use, such that foot use praxis does not benefit from apriori left specialization and reorganizes to the right hemisphere in the absence of hands.