Tonic eye movements induced by bilateral and unilateral galvanic vestibular stimulation (GVS) in guinea pigs

► Measured 3D changes in eye position during galvanic vestibular stimulation (GVS). ► Tonic eye movement was twice as large during bilateral versus unilateral GVS. ► Eye movement responses were symmetrical for anodal and cathodal GVS. ► The symmetry is consistent with activation of regularly discharging afferents. ► The 3D tonic eye rotations are consistent with stimulation of otolith afferents.