Asymmetries of representation in the visual system of pigeons.

Although functional asymmetries in the course of visual information processing have been known for a long time in humans as well as in non-human species, the structural basis of these asymmetries is largely unknown. We now report that due to an asymmetry of commissural projections in the pigeon the left nucleus rotundus of the ascending tectofugal visual system predominantly represents inputs from both eyes while the right nucleus rotundus mainly represents the contralateral left eye. We suggest that a comparable organization exists for several asymmetries in humans. A representation of both hemifields can provide the dominant hemisphere with direct access to all stimulus features when objects cross the vertical meridian.