Catch-Up Saccades in Vestibulo-Ocular Reflex Deficit: Contribution of Visual Information?

Area of Science:

• Neuroscience
• Ophthalmology
• Vestibular System

Background:

• Vestibular deficit impairs gaze stabilization during head rotation.
• Catch-up saccades (overt and covert) compensate for this loss.
• Covert saccades, occurring during head movement, suggest multisensory integration.

Purpose of the Study:

• To evaluate the role of visual information in triggering and guiding catch-up saccades in bilateral vestibulopathy.
• To investigate visuo-vestibular mismatch effects on saccade characteristics.

Main Methods:

• Head impulse test in a virtual reality setting with visuo-vestibular mismatch (normal, half, freeze, inverse).
• Recruited 12 patients with bilateral vestibulopathy.
• Analyzed eye and head movements, focusing on first catch-up saccade characteristics.

Main Results:

• Saccade latency increased with greater visuo-vestibular mismatch.
• Percentage of covert saccades decreased with increased visual feedback error.
• Visually discordant saccades (over 50% of trials) were mainly covert and inversely correlated with vestibulo-ocular reflex gain.

Conclusions:

• Visual information significantly impacts catch-up saccade latency and covert saccade proportion.
• Visual information is not the primary multisensory input for covert catch-up saccades in vestibular deficit.
• Proposed new nomenclature: open and closed-loop saccades.