Inter-trial phase coherence of visually evoked postural responses in virtual reality

Area of Science:

• Neuroscience
• Biomechanics
• Human-Computer Interaction

Background:

• Vision is crucial for maintaining balance and triggering counter-movements.
• Body sway, a key indicator of postural control, is typically measured using the center of pressure (COP).
• Visually evoked postural responses (VEPR) are postural adjustments triggered by visual motion stimuli.

Purpose of the Study:

• To investigate visually evoked postural responses (VEPR) using a virtual reality (VR) moving room paradigm.
• To analyze the coupling between simulated self-motion and human postural sway.
• To explore the frequency range and strength of phase-locking in VEPR.

Main Methods:

• Ten healthy subjects were exposed to a virtual reality environment with a sinusoidally oscillating "moving room" visual stimulus.
• Subjects' center of pressure (COP) was measured using a force platform.
• Data analysis involved wavelet analyses and inter-trial phase coherence (ITPC) to quantify postural sway and stimulus coupling.

Main Results:

• Subjects demonstrated significant coupling of their COP to the visual stimulus.
• Inter-trial phase coherence (ITPC) revealed consistent coupling strength across subjects and frequencies, even when spectral power was low.
• Strong phase coupling was observed at 1.5 Hz, exceeding typical frequency ranges for visual-postural sway coupling.

Conclusions:

• Phase-locking is a fundamental mechanism in human visuomotor control.
• VEPR can be reliably induced and quantified using VR moving room paradigms.
• The human postural control system exhibits robust phase-locking capabilities to visual motion stimuli, even at higher frequencies.