Visual effects on the subjective visual vertical and subjective postural head vertical during static roll-tilt

Area of Science:

• Neuroscience
• Human Perception
• Spatial Orientation

Background:

• Spatial orientation relies on gravity, visual, and somatosensory inputs.
• Tilt perception integrates allocentric (gravity, visual) and egocentric (body axis) information.
• Understanding these integrations is crucial for fields like aviation and neurology.

Purpose of the Study:

• To quantify roll-tilt perception using subjective visual vertical (SVV) and subjective postural head vertical (SPHV).
• To investigate the impact of visual information on SVV and SPHV during static roll-tilt.
• To compare the sensitivity of SVV and SPHV to roll-tilt angles and visual conditions.

Main Methods:

• Nine healthy male volunteers participated in a controlled experiment.
• A flight simulator generated various static roll-tilt environments combined with visual stimuli.
• Subjective visual vertical (SVV) and subjective postural head vertical (SPHV) were measured under different conditions.

Main Results:

• SVV showed significant differences across visual conditions and between 0° and ≥20° body roll-tilt.
• SPHV differed significantly between dark and a specific visual condition (20° right roll-tilt).
• Unlike SVV, SPHV error did not significantly vary with body roll-tilt angle across visual conditions.

Conclusions:

• Human susceptibility to spatial disorientation is modulated by roll-tilt angle and visual input.
• The SPHV appears less affected by roll-tilt angle compared to the SVV.
• These findings highlight distinct roles of visual and postural vertical perception in spatial orientation.