The Cortical Magnification Factor and Photopic Vision

Summary 1. The concept of a topographical representation of sensory surfaces on the mammalian cerebral cortex is now well established. Furthermore, there is claimed an expanded representation for those sensory surfaces associated with behavioural specializations. 2. In the case of the visual system, the field of view associated with the retina is projected on to the striate cortex, with the central fovea or point of most acute vision occupying a disproportionately large area of representation. 3. The term ‘cortical magnification factor’, denoted by M, has been introduced to indicate, for a given eccentricity and meridian, the linear distance in mm along the primary visual cortex concerned with each degree of visual field. 4. The quantitative accuracy of this function subsequently has been improved and a relationship established between cortical magnification and visual acuity in man. 5. On the basis of spatio‐temporal investigations across the visual field under levels of photopic adaptation, visual scientists have utilized retino‐cortical magnification to reconcile aspects of structure and function in the human visual system.