title: A simulation study of the degrees of freedom of movement in reaching and grasping.
abstract: The question of independently controlled components in the act of reaching and grasping has attracted interest experimentally and theoretically. Data from 35 studies were recently found consistent with simulated kinematic finger and thumb trajectories optimised for minimum jerk. The present study closely reproduces those trajectories using a discrete-time model based on minimum acceleration. That model was further used to generate two-dimensional trajectories for finger and thumb to reach and grasp an elliptical object with varying position and/or orientation. Orthogonalisation of these four trajectories revealed one degree of freedom when direction of reach was constant and two degrees of freedom when direction of reach varied, irrespective of object distance and orientation. These simulations indicate that reach and grasp movements contain redundancy that is removable by formation of task-dependent synergies. As skilled movement can be planned and executed in a low dimension workspace, control of these independent components lessens central workload.
authors.affiliation: Neuroengineering Laboratory, School of Electrical Engineering and Telecommunications, University of New South Wales, Sydney 2052, Australia.
authors.forename: Jianming
authors.initials: J
authors.lastname: Jiang
authors.forename: Yueshi
authors.initials: Y
authors.lastname: Shen
authors.forename: Peter D
authors.initials: PD
authors.lastname: Neilson
mesh_terms: D000465:Algorithms; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D018737:Hand Strength; D006801:Humans; D009949:Orientation; D011597:Psychomotor Performance; D011930:Reaction Time