Viewing distance dependence of the vestibulo-ocular reflex during translation: extra-otolith influences.

Despite nearly perfect gaze stability during natural head movements, the amplitude of the vestibulo-ocular reflex during passive head and body translation (TVOR) has been consistently reported to be undercompensatory during near target viewing. Here we have compared the rhesus monkey TVOR during pure head and body translation with the eye movements generated during eccentric yaw rotations, where both semicircular canal and otolith signals are activated. We found a significant increase in both the near target TVOR amplitude and its viewing distance dependence during eccentric rotations, as compared to pure translations. We conclude that the simultaneous activation of the horizontal semicircular canals result in an improvement of the viewing distance-dependence of the rhesus monkey TVOR.