Ocular counter-rolling during active head tilting in humans.

Human ocular counter-rolling has been measured by means of an infra-red video based system: EMIRAT. This method of three-dimensional eye angular displacement recording has an overall precision of 0.5 degrees, is calibrated and is completely non-invasive. Dynamic counter-rolling gain is about 0.5, increasing with head roll oscillation frequency from 0.3 at 0.1 Hz, to 0.7 at 1 Hz. Otolithic contribution to this reflex has been taken into consideration.