Head motion predictability explains activity-dependent suppression of vestibular balance control.

Area of Science:

• Neuroscience
• Biomechanics
• Human Motor Control

Background:

• Vestibular system plays a crucial role in maintaining balance.
• Locomotion involves dynamic adjustments in sensory weighting for balance control.
• A feed-forward balance mechanism using locomotor efference copies is hypothesized.

Purpose of the Study:

• To investigate the dynamic interplay between vestibular input and balance control during human locomotion.
• To determine if head movement predictability influences vestibular signal processing during walking.
• To test the hypothesis of selective vestibular suppression in favor of predictive motor control.

Main Methods:

• 10 healthy subjects underwent stochastic vestibular stimulation (SVS) during standing and walking at various speeds.
• Body sway (center-of-pressure, COP) and head movement predictability (HMP) were measured.
• Correlation analysis quantified the coupling between SVS and COP responses, and HMP was analyzed across the gait cycle.

Main Results:

• Vestibular-to-body sway (SVS-COP) coupling significantly decreased with increasing walking speed.
• Head movement predictability (HMP) increased with faster locomotion.
• SVS-COP coupling exhibited phase-dependent modulation, being lowest during periods of high HMP.

Conclusions:

• Locomotion dynamically down-weights vestibular information, particularly at higher speeds.
• Increased head movement predictability during locomotion supports a shift towards feed-forward balance control.
• Findings suggest that the brain uses locomotor efference copies to predict and regulate balance, reducing reliance on vestibular cues during self-motion.