Fixation suppression of optokinetic nystagmus modulates cortical visual-vestibular interaction.

Water activation positron emission tomography and statistical group analysis were used to evaluate differences in activation-deactivation patterns during small-field visual motion stimulation, eliciting rightward optokinetic nystagmus and its fixation suppression in 12 healthy volunteers. Bilateral patterns of activation in the visual cortex, including the motion-sensitive area MT/V5, and deactivations in an assembly of vestibular areas (posterior insula, thalamus, anterior cingulate gyrus) during optokinetic nystagmus was markedly diminished or totally absent during its fixation suppression. This finding agrees with the concept of a reciprocal inhibitory interaction between the visual-optokinetic and the vestibular systems, which takes place at a lower level during fixation suppression, because the potential mismatch between the two sensory inputs, visual and vestibular, is then reduced.