Motion processing: Where is the naso-temporal asymmetry?

The visual system incorporates a phylogenetically ancient subsystem that responds to overall movement of the retinal image. Its signals induce animals to turn their eyes, heads or bodies to correct the perturbing motion and keep the image as stable as possible. Human optokinetic nystagmus (OKN) is an example: if the eyes are presented with largefield movement, such as the view from the window of a moving train, they go into a repetitive cycle of following the movement, rapidly flicking back and following the movement again.