The Neural Control of Visually Guided Eye Movements
C. Cortical Mechanisms of Visually Guided Saccadic Eye Movements

The next question is what happens when both the frontal eye fields and the superior colliculi are removed. This produced dramatic results as shown in Figure 13. Monkeys were trained to pick out apple pieces placed into slots of different orientations on what we called an "apple board." This figure shows the fixations the monkey made while performing this task repeatedly. Bilateral frontal eye field (FEF) or bilateral superior colliculus (SC) lesions produced relatively small deficits. However, when both structures were removed bilaterally, there was a dramatic deficit: monkeys could no longer target the stimuli with their eyes even though they continued to remove and eat the apple pieces. Animals in which removal of these structures was complete, there were practically no eye movements generated to visual targets. Thus when the superior colliculus and the frontal eye fields are both removed, visually guided eye movements are eliminated. This suggests that these two structures are essential components for the generation of visually guided eye-movements.