Suppression of Optokinetic Velocity Storage in Humans by Static Tilt in Pitch

The effects of static tilts about the pitch axis on human horizontal optokinetic afternystagmus OKAN (HOKAN) were examined. Static tilts in pitch produced tilt-dependent HOKAN suppression. The slow decay (indirect pathway) component (coefficient C and long time constant 1/D) of the two-component model for OKAN was significantly reduced, while the short decay (direct pathway) component (coefficient A and short time constant 1/B) remained invariant as angle of tilt was increased. These results provide further evidence that otolith organ activity can couple to horizontal velocity storage in humans; in accordance with models proposed in the literature.