The neural representation of visual space

TLDR: It is reported here that estimates of Dr are obtained and their usefulness as predictors of M are examined and they are summarised in three basic equations.

Abstract: THE approximate form of the projection of visual space on the striate cortex in man has long been established from neurological evidence1–3 and estimates of cortical magnification M (the extent of striate cortex in millimetres corresponding to a degree of arc in visual space) have been derived from studies on cortical phosphenes and visual acuity4, and migraine scotoma dimensions5. The possibility that M could be estimated from the density of retinal ganglion cells which provide the output from the eye to the brain has received support from studies on monkeys6–8. It has been shown that M is proportional to √Dc (where Dc is the projected ganglion cell density in cells per solid degree of visual space) for peripheral angles (θ) greater than 10°. More centrally, where Dc is maximal, this relationship breaks down because the cells are displaced from their receptive fields by an amount which is difficult to determine8. If data on ganglion cell receptive field density, Dr (in receptive fields per solid degree) were available, they might be expected to relate to M at every point in the visual field. I report here that I have obtained such estimates of Dr and examined their usefulness as predictors of M. The results are summarised in three basic equations.