Plasticity of responses to off-vertical axis rotation

This study assessed whether a change in the magnitude of the angular vestibulo-ocular reflex (VOR) influences the magnitude of the linear VOR, thereby suggesting a common gain element for these reflexes. The responses to linear acceleration using yaw off-vertical axis rotation (OVAR) at 30 degrees tilt were recorded before and after an adaptation protocol designed to increase the angular VOR gain. Subjects included eight asymptomatic healthy young individuals. Eye movements, recorded with electro-oculography, were analyzed to yield gain of the horizontal angular VOR and the magnitude of the modulation and bias components of the response to OVAR. Results indicated that there was no consistent influence of angular VOR gain on the eye movement response to OVAR. Since previous studies have shown that responses to earth horizontal axis rotation are influenced consistently by angular VOR gain, our study suggests that high intensity otolithic stimulation is required to observe changes in the linear VOR following modification of the angular VOR.