Functional MRI mapping of occipital and frontal cortical activity during voluntary and imagined saccades

We investigated the activation of frontal and occipital cortical areas in 14 normal volunteers during voluntary saccades in light or dark and during imagined saccades using functional magnetic resonance imaging (FMRI) with electro-oculogram monitoring. Voluntary saccades in light or dark and imagined saccades led to a significant activation (p < 0.005) of the precentral and posterior medial frontal gyrus (frontal eye field). The medial part of the superior frontal gyrus (supplementary eye field) also showed significant activity during voluntary saccades in all subjects, but only in four subjects during imagined saccades. In addition to frontal activity we found an activated primary visual cortex during voluntary saccades, both in light and in dark. In contrast to executed saccades, imagined eye movements revealed no occipital response under either condition. Our FMRI study supports the concept of frontal eye fields during voluntary saccades and demonstrates that occipital areas are associated with the generation of voluntary eye movements. However, the primary visual cortex is not active when eye movement is only imagined.