The Neural Control of Visually Guided Eye Movements

C. Cortical Mechanisms of Visually Guided Saccadic Eye Movements

vector code vs. place code at six cortical areasNumerous cortical areas are involved in the generation of saccadic eye movements. Figure 6 shows the monkey brain and the major regions from which electrical stimulation elicits saccadic eye movements. The insets show the saccades elicited with the dots representing the direction of the gaze prior to stimulation. At most sites the saccades produced have a fixed vector. What that vector is depends on where one stimulates within the structure just as in the superior colliculus. The visual field representation and the saccadic vectors produced are laid out in a neat topographic order within each structure. Exceptions to vector representation are seen in a frontal region called the medial eye fields (MEF) and in parts of parietal cortex. In these areas the final positions of the eye in orbit is coded, hence called a place code. There is an orderly representation of these positions within these structures.