Embodiment guides motor and spinal circuit development in vertebrate embryo and fetus

We investigated whether motor and spinal circuit development in vertebrates can be accounted for by the properties underlying embodiment. We ran computer simulations of zebrafish embryo, canine and human fetus models with biologically plausible musculoskeletal bodies and spinal neural network, and quantitatively characterized their embodiments and movements by analyzing inter-muscle connectivities. In computer simulations in the human and canine fetus models, we found that development of the embodiment causes changes in movements and increases their complexity, corresponding to the same manner as mammalian motor development. Further, we showed that interaction with the environment as structured by the embodiment can drive the self-organization of the spinal circuit and trigger important developmental motor transitions, which engender coordinated side-to-side alternating movements in the zebrafish embryo model and left-right alternation of the legs in the human fetus model. Our results suggest that embodiment possesses a multitude of regularities that can guide early development.