TY - JOUR
T1 - Impedance control is selectively tuned to multiple directions of movement
AU - Kadiallah, Abdelhamid
AU - Liaw, Gary
AU - Kawato, Mitsuo
AU - Franklin, David W.
AU - Burdet, Etienne
PY - 2011/11
Y1 - 2011/11
N2 - Humans are able to learn tool-handling tasks, such as carving, demonstrating their competency to make movements in unstable environments with varied directions. When faced with a single direction of instability, humans learn to selectively co-contract their arm muscles tuning the mechanical stiffness of the limb end point to stabilize movements. This study examines, for the first time, subjects simultaneously adapting to two distinct directions of instability, a situation that may typically occur when using tools. Subjects learned to perform reaching movements in two directions, each of which had lateral instability requiring control of impedance. The subjects were able to adapt to these unstable interactions and switch between movements in the two directions; they did so by learning to selectively control the end-point stiffness counteracting the environmental instability without superfluous stiffness in other directions. This finding demonstrates that the central nervous system can simultaneously tune the mechanical impedance of the limbs to multiple movements by learning movement-specific solutions. Furthermore, it suggests that the impedance controller learns as a function of the state of the arm rather than a general strategy.
AB - Humans are able to learn tool-handling tasks, such as carving, demonstrating their competency to make movements in unstable environments with varied directions. When faced with a single direction of instability, humans learn to selectively co-contract their arm muscles tuning the mechanical stiffness of the limb end point to stabilize movements. This study examines, for the first time, subjects simultaneously adapting to two distinct directions of instability, a situation that may typically occur when using tools. Subjects learned to perform reaching movements in two directions, each of which had lateral instability requiring control of impedance. The subjects were able to adapt to these unstable interactions and switch between movements in the two directions; they did so by learning to selectively control the end-point stiffness counteracting the environmental instability without superfluous stiffness in other directions. This finding demonstrates that the central nervous system can simultaneously tune the mechanical impedance of the limbs to multiple movements by learning movement-specific solutions. Furthermore, it suggests that the impedance controller learns as a function of the state of the arm rather than a general strategy.
KW - Adaptation
KW - Internal model
KW - Stiffness
KW - Unstable dynamics
UR - http://www.scopus.com/inward/record.url?scp=80755181463&partnerID=8YFLogxK
U2 - 10.1152/jn.00079.2011
DO - 10.1152/jn.00079.2011
M3 - Article
C2 - 21849617
AN - SCOPUS:80755181463
SN - 0022-3077
VL - 106
SP - 2737
EP - 2748
JO - Journal of Neurophysiology
JF - Journal of Neurophysiology
IS - 5
ER -