Cortical magnification, scale invariance and visual ecology.

The visual world of an organism can be idealized as a sphere. Locomotion towards the pole causes translation of retinal images that is proportional to the sine of eccentricity of each object. In order to estimate the human striate cortical magnification factor M, we assumed that the cortical translations, caused by retinal translations due to the locomotion, were independent of eccentricity. This estimate of M agrees with previous data on magnifications, visual thresholds and acuities across the visual field. It also results in scale invariance in which the resolution of objects anywhere in the visual field outside the fixated point is about the same for any viewing distance. Locomotion seems to be a possible determinant in the evolution of the visual system and the brain.