Cortical control of saccadic eye movements as assessed by functional magnetic resonance imaging

In humans, anatomy and physiology of the saccadic eye movement (SEM) system have been studied by invasive techniques that suffer from limited spatial resolution. Functional magnetic resonance imaging (fMRI) provides maps of human brain activations with high spatial resolution. This technique is based on the increase of magnetic resonance signal in cerebral areas activated during a task or a stimulation. Six healthy volunteers underwent fMRI examination while performing visually guided and memory-guided saccades and antisaccades. To assess the activation areas we used a dedicated software for image statistical analysis including z-score, t-test, correlation and cluster activation analysis. Activation areas were found in cortical areas involved in SEM planning and execution, such as the frontal eye fields, the supplementary eye fields, the prefrontal cortex, the parietal eye fields, the striate and the extra-striate cortex. The activation areas showed considerable spatial interindividual variability and no or slight pattern differences between saccade tasks. The high spatial resolution of fMRI allowed the location of the frontal eye fields in the banks and fundus of the precentral sulcus. as well as the location of the parietal eye fields in the intraparietal sulcus. We anticipate that fMRI will provide new insights into the understanding of SEM control.