title: The rules of tool incorporation: Tool morpho-functional & sensori-motor constraints.
abstract: Previous studies showed that using tools modifies the agent's body and space representation. However, it is still not clear which rules govern those remapping processes. Here, we studied the differential role played by the morpho-functional characteristics of a tool and the sensori-motor constraints that a tool imposes on the hand. To do so, we asked a group of participants to reach and grasp an object using, in different conditions, two different tools: Pliers, to be acted upon by the index and thumb fingertips, and Sticks, taped to the same two digits. The two tools were equivalent in terms of morpho-functional characteristics, providing index finger and thumb with the same amount of elongation. Crucially, however, they imposed different sensori-motor constraints on the acting fingers. We measured and compared the kinematic profile of free-hand movements performed before and after the use of both devices. As predicted on the basis of their equivalent morpho-functional characteristics, both tools induced similar changes in the fingers (but not the arm) kinematics compatible with the hand being represented as bigger. Furthermore, the different sensori-motor constraints imposed by Pliers and Sticks over the hand, induced differential updates of the hand representation. In particular, the Sticks selectively affected the kinematics of the two fingers they were taped on, whereas Pliers had a more global effect, affecting the kinematics of hand movements not performed during the use of the tool. These results suggest that tool-use induces a rapid update of the hand representation in the brain, not only on the basis of the morpho-functional characteristics of the tool, but also depending on the specific sensori-motor constraints imposed by the tool.
authors.affiliation: ImpAct Team, Lyon Neuroscience Research Center, INSERM U1028, CNRS UMR5292, 69000 Lyon, France; University of Lyon, 69000 Lyon, France; Hospices Civils de Lyon, Hôpital Neurologique, Mouvement et Handicap & Neuro-immersion, Lyon, France; The Brain and Mind Institute, University of Western Ontario, London, Ontario, Canada. Electronic address: lcardin4@uwo.ca.
authors.forename: L
authors.initials: L
authors.lastname: Cardinali
authors.affiliation: Aging Research Center, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, 11330 Stockholm, Sweden.
authors.forename: C
authors.initials: C
authors.lastname: Brozzoli
authors.affiliation: Department of Statistical Sciences, University of Padua, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Finos
authors.affiliation: University of Lyon, 69000 Lyon, France; Laboratoire Dynamique Du Langage, CNRS UMR5596, Lyon, France.
authors.forename: A C
authors.initials: AC
authors.lastname: Roy
authors.affiliation: ImpAct Team, Lyon Neuroscience Research Center, INSERM U1028, CNRS UMR5292, 69000 Lyon, France; University of Lyon, 69000 Lyon, France; Hospices Civils de Lyon, Hôpital Neurologique, Mouvement et Handicap & Neuro-immersion, Lyon, France.
authors.forename: A
authors.initials: A
authors.lastname: Farnè
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D001828:Body Image; D005260:Female; D018737:Hand Strength; D006801:Humans; D008297:Male; D011597:Psychomotor Performance; D053001:Tool Use Behavior / Q000502:physiology*; D055815:Young Adult
keywords: Body schema; Kinematics; Plasticity; Tool-use