The suppression of cervico-ocular response by the haptokinetic information about the contact with a rigid, immobile...

Horizontal eye movements were recorded in eight healthy subjects during super-slow trunk rotation with respect to the space-stationary head. In some trials, subjects simultaneously indicated their perception of self-motion by means of a joystick. Over the frequency range employed (0.007-0.05 cycles per second, +/- 20 degrees), all subjects perceived the relative motion of head and trunk as a head rotation with respect to the stationary trunk. Eye movements were observed which were in phase with imaginary head rotation; their amplitude exceeded the amplitude of actual body rotation. The grasping of a rigid ground-based handle (1) produced a sensation of trunk rotation in space, (2) suppressed the sensation of imaginary head rotation in space and (3) gave rise to a significant decrease in amplitude of eye movements. The grasping of a stiff rod with non-zero compliance did not produce these effects. It is concluded that eye movements in response to body rotation with respect to the fixed head are not purely reflex reactions, but are influenced by the internal representation of body motion.