Aperçu de la plasticité de la représentation corporelle après l'utilisation d'outils : le rôle de la vision et de la proprioception.
Salam Bahmad · HAL (Le Centre pour la Communication Scientifique Directe) · 2020
Tool-use is an essential component of the human behavioral repertory that allows us to extend the frontiers of our interaction with the environment. Several studies have shown that the use of a tool functionally extending arm length might change the arm representation toward a tool incorporation, inducing what is reported in the literature as a plasticity of the body representation for action. In my doctoral dissertation, I first investigated the contribution of proprioception in the paradigm of tool incorporation by assessing which proprioceptive modality is crucial for this incorporation in an elderly population whose online proprioception remains intact while offline, remembered proprioception is impaired. To this end, we compared the kinematic of reach and grasp movement performed before and after a tool-use session in which 60 years old participants were required to perform the same movements with a mechanical grabber. Results showed that participants modified the kinematic of the transport component of their movement to incorporate the tool as reported previously in younger adults. Most importantly, the kinematic incorporation of the tool was correlated to participant’s online proprioception acuity so that a better online proprioceptive acuity give rise to larger kinematics effects of tool-use. In the second part of my thesis, I wanted to examine how the use of a tool may modify the proprioception acuity itself. To this aim, I assessed the proprioception acuity through a Joint Position Sense test (JPS) in healthy adults, before and after tool-use. Strikingly, proprioception is more precise after tool-use. To confirmed tool incorporation in the arm representation after tool-use, I ran a second experiment in which I measured proprioceptive acuity before and after tool-use and, in addition, we asked participants to localize tactile stimuli delivered to their forearm before and after the use of the tool. The results showed that using a tool induces proprioceptive improvement for the arm that manipulates it that coexist with an updated representation of the arm that used the tool to be elongated. Finally, to examine the role of vision, I assessed the kinematic behavior of two blind populations, a congenitally blind group and a group of later onset. Participants performed a reach and grasp paradigm before and after tool-use to determine whether having experienced vision during youth is an absolute requirement for body representation plasticity to occur. In the two groups alike, we observed no kinematic modifications of arm reaching after tool-use. These results are in sharp contrast with those reported previously in healthy blindfolded participants and stresses the importance of vision during childhood and adolescence to enable tool incorporation in the body state estimate. Finally, in the discussion part I will go throw all my work to relate the results under the umbrella of body representation plasticity after tool-use.