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 con trol of saccadic and smooth-pursuit eye movements. For both functions, a la rgely overlapping network of fronto-parietal and cerebellar areas could be delineated which was equally well or even more activated by covert shifts o f the attentional focus without the performance of eye movements. Imaging o f 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 supplemen tary eye fields (FEF, PEF, SEF) are the key structures for the initiation o f voluntary and reflexive saccades, and of covert attentional shifts. Sacca de-specific functions could be demonstrated only for the FEF and SEF (sacca dic 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 extr astriate visual areas are also involved. It is controversial whether saccad es and smooth-pursuit movements activate different compartments of these ar eas. In the cerebellum, both functions activate the posterior vermis, where as additional activation of the paravermal and lateral hemispheres rather r eflects the cognitive processes involved, such as directed visuo-spatial at tention.