Head positioning control in a gravito-inertial field and in normal gravity.
The way in which the head is controlled in roll was investigated by dissociating the body axis and the gravito-inertial force orientation. Seated subjects (N = 8) were requested to align their head with their trunk, 30 degrees to the left, 30 degrees to the right or with the gravito-inertial vector, before, during (Per Rotation), after off-center rotation and on a tilted chair without rotation (Tilted). The gravito-inertial vector angle during rotation and the chair tilt angle were identical (17 degrees ). The subjects were either in total darkness or facing a visual frame that was fixed to the trunk. Both final error and within-subject variability of head positioning increased when the body axis and the gravito-inertial vector were dissociated (Per Rotation and Tilted). However, the behavior was different depending on whether the subjects were in the Tilted or Per Rotation conditions. The presentation of the visual frame reduced the within-subject variability and modified the perception of the gravito-inertial vector's orientation on the tilted chair. As head positioning with respect to the body and sensing of the gravito-inertial vector are modified when body axis and gravito-inertial vector orientation are dissociated, the observed decrease in performance while executing motor tasks in a gravito-inertial field may be at least in part attributed to the inaccurate sensing of head position.
Sarès
Frédéric
F
UMR 6152 Mouvement & Perception, Université de la méditerranée & CNRS, Faculté des Sciences du Sport, 13288 Marseille Luminy, France. sares@laps.univ-mrs.fr
Bourdin
Christophe
C
Prieur
Jean-Michel
JM
Vercher
Jean-Louis
JL
Menu
Jean-Pierre
JP
Gauthier
Gabriel M
GM
D001696:Biomechanical Phenomena; D003463:Cues; D006112:Gravitation; D019416:Head Movements / Q000502:physiology*; D006801:Humans; D010775:Photic Stimulation; D011187:Posture / Q000502:physiology; D011434:Proprioception; D011597:Psychomotor Performance / Q000502:physiology; D012399:Rotation