Centrifugal pathways to the retina: which way does the "searchlight" point?

This commentary extends the review by Hiroyuki Uchiyama (1989) entitled "Centrifugal pathways to the retina: influence of the optic tectum" Visual Neuroscience 3, 183-206. A further scrutiny is made of the topography of the isthmo-retinal projection of the pigeon, which provides the most fully investigated example of a retinopetal projection. It is suggested that the topographical organization in this system is compatible with it's input being derived from the lower visual field (and upper retina) and it's output being directed to the horizon and lower retina. This is another form of attentional hypothesis for the centrifugal pathway, compatible with a role in ground feeding, and is testable by current tracing techniques in neurobiology.