Inhibition of vestibulo-ocular reflex by tonic stimulation of the posterior neck region in man.

The effect of posterior neck stimulation on vestibulo-ocular reflex (VOR) was studied in 10 healthy subjects. The experimental situation was designed to minimise all afferent inputs except from the neck; each subject was placed in supine position with body fixed to a tilting table inclinable in a vertical plane. The head was immovably secured at 30 degrees to an independent non-inclinable rigid frame. In this situation the body could be mechanically moved upwards in the vertical plane (ventriflexion), producing symmetrical and selective stretch of the posterior neck region. The VOR elicited by caloric monoaural stimulation was evaluated for each of the following static positions: 0 degree and 50 degrees of ventriflexion and vice versa. We observed a significant decrease in the slow-phase angular velocity of induced nystagmus as the body was tilted upwards and a significant opposite effect when the body was returned to the original position. Similar changes in VOR were observed in 4 selected patients with spontaneous 'peripheral nystagmus'. Mechanisms involved in the cervical control of VOR are discussed