Proprioceptive Adaptation and Aftereffects

Until relatively direct interfaces with brain signals become widely available, users will have to play a physically active part in controlling the virtual environment (VE). This involves moving the head, eyes, limbs, or whole body. Control and perception of movement depend heavily on proprioception, which is traditionally de˜ned as the sensation of limb and whole body position and movement derived from somatic mechanoreceptors. This chapter presents evidence that proprioception actually is computed from somatic (muscle, joint, tendon, skin, vestibular, visceral) sensory signals, motor command signals, vision, and audition. Experimental manipulation of these signals can alter the perceived spatial position and movement of a body part, attributions about the source and

33.1 Introduction .......................................................................................................................... 835 33.2 Proprioception, Motor Control, and Spatial Orientation ...................................................... 836

33.2.1 Multisensory and Motor Factors ............................................................................... 836 33.2.2 Sensorimotor Calibration .......................................................................................... 837 33.2.3 Muscle Spindles ........................................................................................................ 837 33.2.4 Role of Body Schema and Spatial Orientation .........................................................840 33.2.5 Bidirectional Interactions of Visual and Muscle Spindle Inªuences .......................840 33.2.6 Role of Tactile Cues in Unifying Muscle Spindle and Other Sensory Inªuences .... 841

33.3 Proprioceptive Adaptation of the Arm to Visual Displacement ........................................... 842 33.3.1 Sensory Rearrangement ............................................................................................ 842 33.3.2 Internal Form of Adaptation ..................................................................................... 842 33.3.3 Conditions Necessary for Adaptation to Occur ........................................................844 33.3.4 Retention and Speci˜city of Adaptation ................................................................... 845

33.4 Adaptation to Altered Force Backgrounds ........................................................................... 845 33.4.1 Motor Adaptation to Coriolis Force Perturbations in a Rotating Room ..................846 33.4.2 Motor Adaptation and Force Perception ...................................................................846 33.4.3 Context-Speci˜c Motor Adaptation and Aftereffects in Different Force

Environments ............................................................................................................ 847 33.4.4 Motor Adaptation to Environments versus Local Contexts ..................................... 847 33.4.5 Role of Touch Cues in Motor and Proprioceptive Adaptation..................................848