Responses to Pop-Out Stimuli in the Barn Owl's Optic Tectum Can Emerge through Stimulus-Specific Adaptation.

Natural scenes are often characterized by a dominant orientation, such as the scenery of a pine forest or the sand dunes in a windy desert. Therefore, orientation that contrasts the regularity of the scene is perceived salient for many animals as a means to break camouflage. By actively moving the scene between each trial, we show here that neurons in the retinotopic map of the barn owl's optic tectum specifically adapt to the common orientation, giving rise to preferential representation of odd orientations. Based on this, we suggest a new mechanism for orientation-based camouflage breaking that links active scanning of scenes with neural adaptation. This mechanism may be relevant to pop-out in other species and visual features.