SENSORIMOTOR CEREBRAL ACTIVATION DURING OPTOKINETIC NYSTAGMUS - A FUNCTIONAL MRI STUDY

Self-motion or object motion can elicit optokinetic nystagmus (OKN), w hich is an integral part of dynamic spatial orientation. We used funct ional MR imaging during horizontal OKN to study cerebral activation pa tterns in sensory and ocular motor areas in 10 subjects. We found acti vation bilaterally in the primary visual cortex, the motion-sensitive areas in the occipitotemporal cortex (the middle temporal and medial s uperior temporal areas), and iu areas known to control several types o f saccades such as the precentral and posterior median frontal gyrus, the posterior parietal cortex, and the medial part of the superior fro ntal gyrus (frontal, parietal, and supplementary eye fields). Addition ally, we observed cortical activation in the anterior and posterior pa rts of the insula and in tl-ie prefrontal cortex. Bilateral activation of subcortical structures such as the putamen, globus pallidus, cauda te nucleus, and the thalamus traced the efferent pathways of OKN down to the brainstem. Functional MRI during OKN revealed a complex cerebra l network of sensorimotor cortical and subcortical activation.