Dual processing of visual rotation for bipedal stance control

Area of Science:

• Neuroscience
• Biomechanics
• Human postural control

Background:

• Visual motion ambiguity can trigger self-motion illusions and postural adjustments.
• A Bayesian model predicts reduced postural response gain with increased visual motion speed.
• Previous research indicated decreasing body-movement response gain with faster visual stimuli.

Purpose of the Study:

• To investigate if visual-flow speed influences postural response to discrete visual scene rotation.
• To test the prediction of decreasing postural response gain with increasing visual motion speed.

Main Methods:

• Standing subjects underwent discrete, unidirectional, full-field visual rotations in the frontal plane.
• Visual rotation speed (0.75-48 deg/s) and direction were pseudo-randomly varied.
• Mediolateral body displacements and ground reaction forces were measured.

Main Results:

• Postural response comprised two sequential components with distinct speed dependencies.
• Early component decreased with faster visual rotation, not by gain attenuation but temporal structure changes.
• Later component increased with faster visual rotation.

Conclusions:

• The two components represent different motor functions in bipedal stance control.
• Early response likely minimizes unintended body motion via the balance control system.
• Later response likely aligns the body with gravity through the postural control system.