Prosthetic embodiment: systematic review on definitions, measures, and experimental paradigms

Abstract

The term embodiment has become omnipresent within prosthetics research and is often used as a metric of the progress made in prosthetic technologies, as well as a hallmark for user acceptance. However, despite the frequent use of the term, the concept of prosthetic embodiment is often left undefined or described incongruently, sometimes even within the same article. This terminological ambiguity complicates the comparison of studies using embodiment as a metric of success, which in turn hinders the advancement of prosthetics research. To resolve these terminological ambiguities, we systematically reviewed the used definitions of embodiment in the prosthetics literature. We performed a thematic analysis of the definitions and found that embodiment is often conceptualized in either of two frameworks based on body representations or experimental phenomenology. We concluded that treating prosthetic embodiment within an experimental phenomenological framework as the combination of ownership and agency allows for embodiment to be a quantifiable metric for use in translational research. To provide a common reference and guidance on how to best assess ownership and agency, we conducted a second systematic review, analyzing experiments and measures involving ownership and agency. Together, we highlight a pragmatic definition of prosthetic embodiment as the combination of ownership and agency, and in an accompanying article, we provide a perspective on a multi-dimensional framework for prosthetic embodiment. Here, we concluded by providing recommendations on metrics that allow for outcome comparisons between studies, thereby creating a common reference for further discussions within prosthetics research.

Experience of adults with upper-limb difference and their views on sensory feedback for prostheses: a mixed methods study

“…It should be noted that the interpretation used to describe embodiment in the survey (Makes the prosthesis feel more like a part of the body rather than a tool) is one of several used in the literature. The reader can refer to [ 30 ] and [ 31 ] for more details. “before you start engaging in activity, you know.. its being comfortable with yourself and being comfortable with the way people perceive you” (Walter)

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Embodiment of a virtual prosthesis through training using an EMG-based human-machine interface: Case series

“…The embodiment of an external object is a complex concept and experience. Currently, the literature shows an overlap of terms and definitions ( De Vignemont, 2011 ; Makin et al, 2017 ; Zbinden et al, 2022 ). Here we based our protocol mostly on the definition provided by De Vignemont (2011) ; Makin et al (2017) , where there are more practical aspects to be implemented in the therapeutic context: “the ability to process properties of this object at the sensory, motor and/or affective levels in the same way that the properties of one’s own body parts.” This definition is interesting because it inherently brings an ecological and interactive perspective, where the embodiment of an external object can only be achieved if the subjects systematically interact with the environment (including the object itself) through specific sensorimotor criteria.…”

“…There are studies that have investigated embodiment through psychophysical tests ( Serino et al, 2007 ; Marini et al, 2014 ; Shokur et al, 2016 ), reports and/or electrophysiological activity ( Armel and Ramachandran, 2003 ; Ehrsson et al, 2007 , 2008 ). However, we claim that since different mechanisms are underling and influencing the induction of embodiment ( De Vignemont, 2011 ; Makin et al, 2017 ; Zbinden et al, 2022 ), multiple tasks and measurements are required to cover all embodiment dimensions.…”

“…Therefore, the association of different factors and mechanisms not only enriches the comprehension of the induction and enhancement of embodiment (in this case, of the virtual prosthesis), but they are necessary ( De Vignemont, 2011 ; Makin et al, 2017 ; Zbinden et al, 2022 ).…”

Benefits of the Cybathlon 2020 experience for a prosthetic hand user: a case study on the Hannes system

“…Furthermore, three items of an ad-hoc questionnaire (item 1, 2, 3; subsection ‘Embodiment’), inspired by the RHI questionnaires [ 20 , 24 ], explored the embodiment obtained with Hannes in a subjective way and are shown in Table 1 . The ad-hoc questionnaire was formulated with statements as in [ 25 ] and as the standard validated questionnaires exploited in this evaluation.…”