Cortical localisation of saccades and smooth-pursuit eye movments via functional imaging

In recent years, modern neuroimaging has provided a more precise anatomical localisation and functional characterisation of cortical areas for the control of saccadic and smooth-pursuit eye movements. For both functions, a largely overlapping network of fronto-parietal and cerebellar areas could be delineated which was equally well or even more activated by covert shifts of the attentional focus without the performance of eye movements. Imaging of ocular motor subfunctions by applying specific experimental paradigms in active and control conditions has yielded new insights into the functional specialisation of these areas. The frontal, the parietal, and the supplementary eye fields (FEF, PEF, SEF) are the key structures for the initiation of voluntary and reflexive saccades, and of covert attentional shifts. Saccade-specific functions could be demonstrated only for the FEF and SEF (saccadic sequences). The dorsolateral prefrontal cortex (spatial working memory) and the anterior cingulate cortex (self-paced saccades) are also involved. Key areas for smooth pursuit are the FEF and the V5 complex in the parieto-temporo-occipital junction, but the SEF, the intraparietal sulcus and extrastriate visual areas are also involved. It is controversial whether saccades and smooth-pursuit movements activate different compartments of these areas. In the cerebellum, both functions activate the posterior vermis, whereas additional activation of the paravermal and lateral hemispheres rather reflects the cognitive processes involved, such as directed visuo-spatial attention.