Human Cerebellar Activation in Relation to Saccadic Eye Movements: A Functional Magnetic Resonance Imaging Study

Abstract

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° 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 T₁-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.

Cortical and cerebellar activation induced by reflexive and voluntary saccades

“…The cerebellar hemispheres were bilaterally activated during both voluntary (Dieterich et al 2000) and reXexive saccades (Hayakawa et al 2002). Activation in vermis VI and VII was observed in reXexive saccades (Hayakawa et al 2002;Nitschke et al 2004).…”

“…The cerebellar hemispheres were bilaterally activated during both voluntary (Dieterich et al 2000) and reXexive saccades (Hayakawa et al 2002). Activation in vermis VI and VII was observed in reXexive saccades (Hayakawa et al 2002;Nitschke et al 2004). Dieterich et al proposed that vermis IX and lobules IV and V, as well as a small portion of vermis VIII, might be involved in oculomotor performance and the activation of the cerebellar hemispheres could possibly reXect visuospatial attention processes (Dieterich et al 2000).…”

“…Saccades are fast rotatory eye movements that serve to move the eyes as quickly as possible, so that an object of interest is projected onto the fovea where it can be visually processed in detail (Schall 1995;Hayakawa et al 2002;Schiller and Tehovnik 2005;Amlot and Walker 2006). Saccades can be classiWed into two broad categories: reXexive and higher-order saccades.…”

“…Several functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) imaging studies have shown activation in the human cerebellum during saccadic eye movements (Desmurget et al 1998;Dieterich et al 2000;Hayakawa et al 2002;Nitschke et al 2004). For instance, Hayakawa et al observed activity in the posterior vermis and the bilateral hemispheres of the cerebellum when subjects made saccades between two stationary targets (Hayakawa et al 2002).…”

“…For instance, Hayakawa et al observed activity in the posterior vermis and the bilateral hemispheres of the cerebellum when subjects made saccades between two stationary targets (Hayakawa et al 2002).…”