title: Unconstrained three-dimensional reaching in rhesus monkeys.
abstract: To better understand normative behavior for quantitative evaluation of motor recovery after injury, we studied arm movements by non-injured rhesus monkeys during a food-retrieval task. While seated, monkeys reached, grasped, and retrieved food items. We recorded three-dimensional kinematics and muscle activity, and used inverse dynamics to calculate joint moments due to gravity, segmental interactions, and to the muscles and tissues of the arm. Endpoint paths showed curvature in three dimensions, suggesting that maintaining straight paths was not an important constraint. Joint moments were dominated by gravity. Generalized muscle and interaction moments were less than half of the gravitational moments. The relationships between shoulder and elbow resultant moments were linear during both reach and retrieval. Although both reach and retrieval required elbow flexor moments, an elbow extensor (triceps brachii) was active during both phases. Antagonistic muscles of both the elbow and hand were co-activated during reach and retrieval. Joint behavior could be described by lumped-parameter models analogous to torsional springs at the joints. Minor alterations to joint quasi-stiffness properties, aided by interaction moments, result in reciprocal movements that evolve under the influence of gravity. The strategies identified in monkeys to reach, grasp, and retrieve items will allow the quantification of prehension during recovery after a spinal cord injury and the effectiveness of therapeutic interventions.
authors.affiliation: School of Life Sciences, Center for Adaptive Neural Systems, 427 E. Tyler Mall, LSE 216, Arizona State University, Tempe, AZ 85287-4501, USA. devin.jindrich@asu.edu
authors.forename: Devin L
authors.initials: DL
authors.lastname: Jindrich
authors.forename: Gregoire
authors.initials: G
authors.lastname: Courtine
authors.forename: James J
authors.initials: JJ
authors.lastname: Liu
authors.forename: Heather L
authors.initials: HL
authors.lastname: McKay
authors.forename: Rod
authors.initials: R
authors.lastname: Moseanko
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Bernot
authors.forename: Roland R
authors.initials: RR
authors.lastname: Roy
authors.forename: Hui
authors.initials: H
authors.lastname: Zhong
authors.forename: Mark H
authors.initials: MH
authors.lastname: Tuszynski
authors.forename: V
authors.initials: V
authors.lastname: Reggie Edgerton
mesh_terms: D000818:Animals; D001132:Arm / Q000294:innervation / Q000502:physiology*; D001696:Biomechanical Phenomena / Q000502:physiology; D004551:Elbow Joint / Q000502:physiology; D004576:Electromyography / Q000379:methods; D006112:Gravitation; D006225:Hand / Q000502:physiology; D018737:Hand Strength / Q000502:physiology; D007596:Joints / Q000502:physiology; D008253:Macaca mulatta / Q000502:physiology* / Q000523:psychology; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology; D009483:Neuropsychological Tests / Q000592:standards; D009949:Orientation / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology; D012785:Shoulder Joint / Q000502:physiology; D013028:Space Perception / Q000502:physiology*; D014785:Vision, Ocular / Q000502:physiology*