Differential effects of visual feedback on subjective visual vertical accuracy and precision

Area of Science:

• Neuroscience
• Human Perception
• Vestibular System

Background:

• The brain integrates sensory information to estimate gravitational verticality.
• Subjective visual vertical (SVV) estimates show head-roll dependent errors, particularly the A-/E-effect.
• It is unclear if visual feedback improves SVV accuracy through adaptation or cognitive strategies.

Purpose of the Study:

• To investigate if visual feedback enhances SVV accuracy.
• To determine if accuracy improvements are due to adaptational shifts or cognitive strategies.
• To assess the persistence of feedback-induced accuracy changes.

Main Methods:

• 12 healthy subjects adjusted a luminous arrow to vertical across various head-roll positions (0-120 degrees).
• Visual feedback (lights on, previous adjustment, earth-vertical cross) was provided after each trial.
• Control trials without feedback and a session with consecutive feedback/no-feedback blocks were conducted.

Main Results:

• Visual feedback significantly reduced errors at large head-roll angles (90-120 degrees), decreasing under-compensation.
• SVV precision was not significantly affected by visual feedback.
• Error reduction persisted for at least 18-24 minutes after feedback removal.
• Most subjects reported consciously applying a bias based on feedback.

Conclusions:

• Visual feedback improves SVV accuracy primarily through a cognitive strategy, not by altering the internal verticality estimate.
• The underlying mechanisms of SVV perception remained stable, as evidenced by unaffected precision.
• Cognitive adjustments, rather than sensory adaptation, explain the enhanced accuracy and its persistence.