The ability of using a large variety of tools is important in our daily life. Behind human tool-use abilities lays the brain capacity to incorporate tools into the body representation for action (Body Schema, BS), thought to rely mainly on proprioceptive information. Here we tested whether tool incorporation is possible in absence of proprioception by studying a patient with right upper-limb deafferentation. We adopted a paradigm sensitive to changes of the Body Schema and analysed the kinematics of free-hand movements before (...) and after tool-use, in three sessions over a period of two years. In the first session, before tool-use, the kinematics of the deafferented hand was disrupted. Similarly, the first movements with the tool (a mechanical grabber elongating the arm by ∼40cm) showed an abnormal profile that tended to normalize at the end of the session. Subsequent free-hand movements were also normalised. At session 2, 6 months later, the patient exhibited normal free-hand kinematic profiles, additionally showing changes in grasping kinematics after tool-use, but no sign of tool incorporation. A follow-up two years later, further confirmed the normalized kinematic profile but the absence of tool incorporation. This first description of tool-use in absence of proprioception shows the fundamental role of proprioception in the update of the Body Schema. These results provide an important further step in understanding human motor control and have implications for future development of rehabilitation programs for patients with sensory deficits. (shrink)

Body representations are known to be dynamically modulated or extended through tool use. Here, we review findings that demonstrate the importance of a user's tool experience or expertise for successful tool embodiment. Examining expert tool users, such as individuals who use tools in professional sports, people who use chopsticks at every meal, or spinal injury patients who use a wheelchair daily, offers new insights into the role of expertise in tool embodiment: Not only does tool embodiment differ between novices and (...) experts, but experts may experience enhanced changes to their body representation when interacting with their own, personal tool. The findings reviewed herein reveal the importance of assessing tool skill in future studies of tool embodiment. (shrink)

In our everyday life, we have the genuine feeling that when something we use works very well, we forget that we are doing something that is mediated by something else. It happens when we read through our glasses, or when we drive home, or when we play guitar. In all those cases, it can be said that the device becomes an extension of our body, or that we have incorporated it. In this paper I want to discuss the extension/incorporation dichotomy (...) as presented in contemporary cognitive sciences. I will present the state of the art in the debate in order to promote a methodological shift, namely to adopt two concept borrowed from Material Engagement Theory developed by Lambros Malafouris. By advocating the concepts of temporality and metaplasticity, I will argue for two different but related things: 1) extension and incorporation don’t have to be conceived only spatially, but temporally. This shift leads to two distinctive implications: first, the sooner two entities establish a prosthetic contact, the higher the chances to reach incorporation; second, extension temporally precedes incorporation; the former being an early-staged phenomenon of – a condition of possibility for – the latter. 2) Such a temporal perspective is at the base of metaplasticity, which describes, in the context of MET, the constant, co-constitutive loop between humans and things: metaplasticity deflates the privileged role traditionally attributed to the subject in the making of phenomenal experience. Finally, I will discuss extension and incorporation in media theory, relying on the concept of radical mediation. (shrink)