Cortical activation during optokinetic stimulation – an fMRI study

Abstract

Conclusion: Activation of cortical areas related to visual motion processing and control of eye movement, and deactivation of parieto-insular vestibular cortices (PIVC) were revealed by functional magnetic resonance imaging (fMRI) with small-field optokinetic stimulation (OKS). The results agreed well with those of previous studies, which indicates that the current protocol is reliable enough to be used as a clinical examination. Objectives: To propose an fMRI set-up with OKS that is reliable and simple enough to be performed as a clinical test. Subjects and methods: Ten right-handed healthy volunteers participated in this study. fMRI was used to measure blood oxygen level-dependent (BOLD) signal increases (contrast: OKS – rest) and decreases (contrast: rest – OKS) during small-field OKS. Functional images were acquired using a standard clinical scanner operating at a magnetic field strength of 1.5 T. The data were analyzed by statistical parametric mapping (SPM2), and the significance level was set at p<0.001, uncorrected. Results: BOLD signal increases were observed in the visual association area of both hemispheres (BA19) (MT/V5), primary visual cortex (BA17) of the right hemisphere, bilateral superior parietal lobules (BA7), and bilateral frontal eye fields (BA6). Decreases of BOLD signals were observed in the PIVC bilaterally.

• Optokinetic nystagmus
• visual cortex
• vestibular cortex
• functional MRI