  Motion tracking is a challenge the visual system has to solve by reading out
the retinal population. Here we recorded a large population of ganglion cells
in a dense patch of salamander and guinea pig retinas while displaying a bar
moving diffusively. We show that the bar position can be reconstructed from
retinal activity with a precision in the hyperacuity regime using a linear
decoder acting on 100+ cells. The classical view would have suggested that the
firing rates of the cells form a moving hill of activity tracking the bar's
position. Instead, we found that ganglion cells fired sparsely over an area
much larger than predicted by their receptive fields, so that the neural image
did not track the bar. This highly redundant organization allows for diverse
collections of ganglion cells to represent high-accuracy motion information in
a form easily read out by downstream neural circuits.
