Motor control of voluntary arm movements |
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Authors: | M L Corradini M Gentilucci T Leo G Rizzolatti |
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Institution: | (1) Dipartimento di Elettronica ed Automatica, University of Ancona, Via Brecce Bianche, I-60131 Ancona, Italy;(2) Istituto di Fisiologia Umana, University of Parma, Via Gramsci 14, I-43100 Parma, Italy |
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Abstract: | The motor control of pointing and reaching-to-grasp movements was investigated using two different approaches (kinematic and
modelling) in order to establish whether the type of control varies according to modifications of arm kinematics. Kinematic
analysis of arm movements was performed on subjects' hand trajectories directed to large and small stimuli located at two
different distances. The subjects were required either to grasp and to point to each stimulus. The kinematics of the subsequent
movement, during which subject's hand came back to the starting position, were also studied. For both movements, kinematic
analysis was performed on hand linear trajectories as well as on joint angular trajectories of shoulder and elbow. The second
approach consisted in the parametric identification of the black box (ARMAX) model of the controller driving the arm movement.
Such controller is hypothesized to work for the correct execution of the motor act. The order of the controller ARMAX model
was analyzed with respect to the different experimental conditions (distal task, stimulus size and distance). Results from
kinematic analysis showed that target distance and size influenced kinematic parameters both of angular and linear displacements.
Nevertheless, the structure of the motor program was found to remain constant with distane and distal task, while it varied
with precision requirements due to stimulus size. The estimated model order of the controller confirmed the invariance of
the control law with regard to movement amplitude, whereas it was sensitive to target size. |
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