Corrections in grasp posture in response to modifications of action goals

• Published in: PloS one Vol. 7; no. 9; p. e43015
• Main Authors: Hughes, Charmayne M L, Seegelke, Christian, Spiegel, Marnie Ann, Oehmichen, Corinna, Hammes, Julia, Schack, Thomas
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 06.09.2012; Public Library of Science (PLoS)
• Subjects: Action research; Activities of daily living; Adult; Biology; Biomechanical Phenomena - physiology; Brain research; Cognition & reasoning; Comfort; Control theory; Cylinders; Feedforward control; Female; Goals; Grasping; Hand - physiology; Hand Strength - physiology; Humans; Kinematics; Male; Posture; Posture - physiology; Robotics; Social and Behavioral Sciences; Time Factors; Germany
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0043015

There is ample evidence that people plan their movements to ensure comfortable final grasp postures at the end of a movement. The end-state comfort effect has been found to be a robust constraint during unimanual movements, and leads to the inference that goal-postures are represented and planned prior to movement initiation. The purpose of this study was to examine whether individuals make appropriate corrections to ensure comfortable final goal postures when faced with an unexpected change in action goal. Participants reached for a horizontal cylinder and placed the left or right end of the object into the target disk. As soon as the participant began to move, a secondary stimuli was triggered, which indicated whether the intended action goal had changed or not. Confirming previous research, participants selected initial grasp postures that ensured end-state comfort during non-perturbed trials. In addition, participants made appropriate on-line corrections to their reach-to-grasp movements to ensure end-state comfort during perturbed trials. Corrections in grasp posture occurred early or late in the reach-to-grasp phase. The results indicate that individuals plan their movements to afford comfort at the end of the movement, and that grasp posture planning is controlled via both feedforward and feedback mechanisms.