Human cerebellar activation in relation to saccadic eye movements: a functional magnetic resonance imaging study.

PURPOSE: The functional organization of the human cerebellum involved in saccadic eye movements was investigated using functional magnetic resonance imaging (fMRI). METHODS: The subjects were 7 normal volunteers aged 18-34 years. Visual stimuli were back-projected onto a screen placed at the subjects' feet. The stimulation period of 30 s consisted of a saccade target jumping back and forth horizontally by 20 degrees once per second. The control period of 30 s consisted of a fixed target. The stimulation and control periods were alternated 10 times during the presentation. Functional images were collected with a 1.5-tesla clinical MRI scanner. The significance of activation was determined by Statistical Parametric Mapping (SPM 99) at a threshold of p < 0.001 (uncorrected), and significantly activated areas were superimposed on the T(1)-weighted images. RESULTS: Significantly activated areas related to visually guided saccades were observed in the cerebellar vermis (declive and folium), in the bilateral cerebellar hemispheres (mainly the superior semilunar lobule) of the cerebellum, in the frontal eye field, in the supplementary eye field and in parts of the parietal lobule of the cerebrum. CONCLUSION: Our results suggest that the cerebellar posterior vermis and bilateral hemispheres are related to saccades in humans. These results are consistent with neurophysiological data obtained in primates.