Kyungji Moon¹ (), Florencia Martinez-Addiego¹, Yuqi Liu^1,2, Maximilian Riesenhuber^1,3, Jody C. Culham^4,5, Ella Striem-Amit¹; ¹Georgetown University Medical Center, ²Institute of Neuroscience, Key Laboratory of Primate Neurobiology, CAS Center for Excellence in Brain Sciences and Intelligence Technology, Chinese Academy of Sciences, ³Center for Neuroengineering, Georgetown University, ⁴Department of Psychology, University of Western Ontario, ⁵Brain and Mind at Western, Western Interdisciplinary Research Building, University of Western Ontario

What are the mechanisms for understanding tool-use actions? To what extent do we generalize across various parameters, such as acting body part, in the observed actions? Here, we tested if there is a shared neural substrate for observed tool-use actions regardless of if they are performed with the hand or with the foot. We leveraged functional neuroimaging in typically-developed controls and individuals born without hands to understand whether there are shared representations for tool-use, regardless of the observed executing body part, and regardless of one’s motor experience. fMRI data from control subjects (n=18) and people born without hands (n=7) were collected while participants passively viewed complex and simple tool-use actions performed with either the hand or foot. We found shared neural responses across the observed body part for both typically-developed individuals and individuals born without hands, which suggested that observed tool-use actions are represented independently of both observed body part and personal sensorimotor experience. Specifically, univariate analyses revealed a consistent preference for action-type (simple or complex tool-use) regardless of observed executing body part in the left superior parietal lobe (SPL) for both typically-developed individuals and people born without hands. Further, multi-voxel pattern analysis successfully discriminated between observed simple and complex tool-use actions consistently across the body part in the bilateral SPL, inferior parietal lobe (IPL), and lateral occipitotemporal cortex (LOTC). Together the results suggest there are shared neural substrates for action understanding regardless of observed body part that are consistently differentiated in typically-developed individuals and people born without hands. This supports generalization across body parts in action perception and implies that motor experience is not necessary for core action understanding.

Acknowledgements: This work was supported by the Edwin H. Richard and Elisabeth Richard von Matsch Distinguished Professorship in Neurological Diseases (to E.S.A.).