Galvanic vestibular stimulation in humans: effects on otolith function in roll

Area of Science:

• Neuroscience
• Ophthalmology
• Vestibular System

Background:

• The vestibular system, particularly the otolith organs, plays a crucial role in sensing head position and motion.
• Understanding how external stimuli affect vestibular input is essential for diagnosing and treating balance disorders.

Purpose of the Study:

• To investigate the effects of unilateral galvanic vestibular stimulation (GVS) on ocular torsion and subjective visual tilts.
• To determine if GVS influences static otolith input in the roll plane.

Main Methods:

• Twelve healthy subjects received unilateral galvanic vestibular stimulation via electrodes on the mastoid.
• Measurements included ocular torsion, peripheral visual field tilt, and foveal vertical line tilt.
• The correlation between stimulation intensity and measured parameters was analyzed.

Main Results:

• Anodal stimulation of the right mastoid induced ipsiversive tonic ocular torsion (0.5-3.7 degrees).
• Contralateral tilts of the peripheral visual field (1-9 degrees) and foveal vertical line (0.5-6.2 degrees) were observed.
• A positive correlation was found between stimulation strength and the magnitude of all measured effects.

Conclusions:

• Unilateral GVS induces ocular torsion and visual tilts, indicating a stimulus-induced tonic otolith imbalance.
• These findings demonstrate that GVS affects static otolith input in the roll plane, in addition to dynamic semicircular canal input.