A multi-dimensional framework for prosthetic embodiment: Review and perspective for translational research

The concept of embodiment has gained widespread popularity within prosthetic research. Embodiment has been claimed to be an indicator for the efficacy of sensory feedback and control strategies. Moreover, it has even been claimed to be necessary for prosthetic acceptance, albeit unfoundedly. Despite the popularity of the term, an actual consensus on how prosthetic embodiment should be used in an experimental framework has yet to be reached. The lack of consensus is in part due to terminological ambiguity and the lack of an exact definition of prosthetic embodiment itself. In a review published parallel to this article, we summarized the definitions of embodiment used in the prosthetics literature and concluded that treating prosthetic embodiment as a combination of ownership and agency allows for embodiment to be quantified, and thus useful in translational research. Here, we reviewed the potential mechanisms that give rise to ownership and agency considering temporal, spatial, and anatomical constraints. We then use this to propose a multi-dimensional framework where prosthetic embodiment arises within a spectrum dependent on the integration of volition and multi-sensory information as demanded by the degree of interaction with the environment. This framework allows for different experiments on sensory feedback and control to be put into perspective. Considering embodiment in a spectrum tied to the interaction with the environment led us to conclude on the importance of evaluating prosthetic technologies operating in environments as close to daily life as possible.