Body-tilt and visual verticality perception during multiple cycles of roll rotation

Area of Science:

• Neuroscience
• Human Physiology
• Vestibular System

Background:

• The vestibular system, particularly the semicircular canals, provides crucial information for spatial orientation.
• Degradation of canal cues during prolonged motion can impact spatial perception.
• Understanding how the brain integrates sensory information under dynamic conditions is vital.

Purpose of the Study:

• To investigate how human spatial orientation judgments, specifically the subjective visual vertical (SVV) and subjective body tilt (SBT), are affected by decaying vestibular canal cues during constant velocity roll rotation.
• To compare dynamic SVV and SBT performance across multiple rotation cycles and with static conditions.

Main Methods:

• Participants performed subjective visual vertical (SVV) and subjective body tilt (SBT) tasks during three cycles of constant-velocity roll rotation.
• SVV and SBT were assessed across the entire tilt range.
• Static SVV responses were also recorded for comparison.

Main Results:

• Dynamic SVV responses showed a systematic bias towards the head pole (A-effect) as tilt increased, with a bimodal pattern (A- and E-effects) near inversion.
• This tilt-dependent error pattern repeated across rotation cycles without significant worsening.
• Dynamic SBT errors were minimal and unimodal, suggesting visual-verticality errors were not due to body-tilt misestimation.

Conclusions:

• The egocentric bias mechanism in spatial orientation becomes more prominent during constant velocity roll rotation as canal signals decay.
• Perceptual errors in disambiguating otolith signals are minimal, even with reduced canal input.
• The findings support a canal-otolith interaction model with adaptations for dynamic spatial orientation.