The orientation of sensors toward regions of interest of the environment is an important motor activity, monitored by ancient struc- tures of the brainstem. Particularly, the superior colliculus is known to be deeply involved in visual saccadic behavior. Target selection relies on various hints including exogenous information about the nature and the position of candidate targets and endogenous information about current motivations. We present a model of the collicular structure based on bio- logical data, the speci city of which is related to the homogeneity of the underlying substratum of computation. This makes it more suitable to process massive visual ows on a distributed architecture, as it could be requested in a realistic task in autonomous robotics. The present model is restricted to the exogenous part of the visual pathway, from the retina to the superior colliculus. A realistic behavior for the selection of exogenous targets is reported here