Static cervico-ocular reflex in healthy humans

Area of Science:

• Ophthalmology
• Neuroscience
• Vestibular System

Background:

• Dynamic cervico-ocular reflex (COR) and vestibulo-ocular reflex (VOR) stabilize retinal images.
• Dynamic COR gain is low in healthy individuals but elevated with vestibular dysfunction.
• Static COR has not been previously observed in healthy individuals.

Purpose of the Study:

• To determine the presence of static COR in healthy individuals.
• To quantify static COR in the roll plane.
• To investigate the relationship between neck flexion and static COR.

Main Methods:

• Eleven healthy participants underwent video oculography to measure eye torsion.
• Static COR was induced by lateral neck flexion during body tilt (15°, 30°, 45°).
• Ocular counterroll (OCR) was compared between whole-body and head tilts.

Main Results:

• Static COR was significantly observed as eye torsion opposite to the direction of body tilt.
• Head tilt OCR was smaller than whole-body tilt OCR on the right side, but not the left.
• The amplitude of static COR increased with greater neck flexion stimulation.

Conclusions:

• Static COR is present in healthy individuals.
• Static COR contributes to visual stability.
• The magnitude of static COR is influenced by the degree of neck flexion.