The human torsional vestibulo-ocular reflex during rotation about an earth-vertical axis

Abstract

Using the magnetic search coil technique, we have measured the gain and time constant ( T vor) of the torsional vestibulo-ocular reflex (VOR) in 4 subjects who were rotated about an earth-vertical axis with their necks extended and faces supine. Following a 1-min period of rotation in darkness at 50°/s, the post-rotational response to a velocity off-step had a group mean gain of 0.43 and T vor of 3.7 s. Following a 1-min period of rotation in the light at 50°/s, the post-rotational response indarkness had a group mean gain of 0.29 and T vor of 4.1 s. Following rotation in darkness with the neck flexed and head prone, the post-rotational response, measured in two subjects, had a mean gain of 0.39 and T vor of 5.7. Similar results were obtained with 100°/s stimuli. In all subjects, the gain and T vor of the torsional VOR were smaller than corresponding values for their horizontal VOR; these smaller values can be related to the different visual demands made of the torsional VOR.