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

The data shown in Figure 23 were obtained while stimulating the medial eye fields (MEF). Stimulation consistently produced facilitation as long as one of the targets was placed into the terminal zone of the stimulated neurons. Since in MEF we have an orbital code, the terminal zone is fixed in space as long as the head is stationary. It is therefore possible to move the entire display so as to place the fixation spot into the terminal zone instead of a target. When that is done, stimulation causes a delay in saccade initiation by increasing fixation time in a fashion similar to that found when those regions of LIP are stimulated that contain fixation cells. Thus areas LIP and MEF appear to play a role in decisions about when to initiate a saccadic eye movement.