Figure 2. Typical subject in different sensory conditions.

Movement of the body (or inverted pendulum) is shown with active adjustments (bias) of the hand (or motor). The left pair of traces (condition A) shows all the sensory modalities in play. The body is balanced by hand with the eyes open so the subject has Proprioceptive (−), Visual and Vestibular information. In the middle pair of traces (condition G) only Vestibular and Proprioceptive (−) information are available because the eyes are closed. In the right hand pair of traces (condition F) only Visual information is available because the subject is stationary and the force is provided by the servomotor.