Saccade induced cortical activation in patients with post-stroke visual field defects

Substantial disability in patients with hemianopia results from reduced visual perception. Several studies have shown that these patients have impaired saccades but may improve search strategies with appropriate training of saccades. We used fMRI to study the representation of saccades in patients with post-stroke hemianopia to the left. Brain activation during visually guided saccades was measured in 10 patients with a pure occipital cortical lesion causing homonymous hemianopia and in 10 healthy control subjects. Differences in activation between rest and saccades and between controls and patients were assessed with statistical parametric mapping (SPM'99). In normal subjects, significant activation was found in the frontal and parietal eye fields bilaterally and in the supplementary eye field. These areas were also activated in patients, however, to a lesser degree. In contrast, an area of increased activation in patients was found in the posterior parietal cortex of the (non-affected) left hemisphere. Visual field defects after striate lesions are associated with changes in the frontoparietal network underlying the cortical control of saccades.