Fig. 8.

Simple scheme of the sensorimotor integration and reweighting processes following addition or withdrawal of V and T during standing. Vestibular, proprioceptive, visual, and haptic (T) information are continuously detected and passed to the brain (top). The different modalities converge at an integrator, which incorporates the different stimuli and transforms them into information for maintaining balance. Following sudden shift in visual and/or haptic state, a variable integration time period occurs before any change in sway level is observed (bottom). Following addition of V (solid black), T (dashed), or both simultaneously (dotted), the integration process reaches the threshold (horizontal dashed line) at which the brain modifies the postural muscle activity at different times according to modality. When both V and T are added, the integration time is the shortest. In the case of withdrawal, the “disintegration” process is faster than addition, being the shortest when both V and T are removed. Once the threshold is reached following addition, CoP oscillation starts decreasing exponentially, reflecting the upweighting of the new stabilizing information and the downweighting of the proprioceptive and vestibular inflow (solid gray). Following withdrawal, the remaining proprioceptive and vestibular inputs are upweighted. a.u., Arbitrary units.