Inertial constraints on limb proprioception are independent of visual calibration

Fundamental to movement control is the perception of limb position by the proprioceptive functions of muscles and tendons, referred to as haptic proprioception. An important basis for the on-line haptic proprioception of a limb\u27s position is the detection of the principal directions of the limb\u27s inertia tensor. When experimental manipulations break the coincidence of the spatial axes of a limb and the principal directions of its inertia tensor, haptic proprioception conforms to the principal directions. Additionally, when prisms break the coincidence between the visual position of the arm and its actual position, perception of limb direction following removal of the prisms is shifted in accordance with the new visual-spatial direction. ^ The present research was directed at the relation between the changes induced in limb proprioception by inertial and visual manipulations. In three experiments, variation of the arms\u27 mass distribution was combined with prism adaptation to investigate the hypothesis that the effects of manipulating a limb\u27s mass distribution and a visually-induced proprioceptive shift would combine additively (would not interact) in determining perceived limb direction. This hypothesis was supported across a broad variety of experimental manipulations, including plane of motion, initial body posture, proprioceptive target location, and proprioceptive experience required during prism adaptation. The major implication is that haptic proprioception depends upon local frames of reference based on the limbs\u27 physical properties that are relative to a broader frame of reference with respect to which the body\u27s position and orientation in the environment are measured.