and attention is conserved across vertebrates all the way to primates 18,19. The functional localization of IOR in humans to an archaic brain structure suggests that the phenomenon may be a universal mechanism that evolved early in evolution to support an efficient search. Support for this notion includes recent studies demonstrating that the basic features of IOR are found in the archer fish 20,21. However, studies in other non-mammalian vertebrates are scarce. In this study, we addressed two questions: 1) Do barn owls possess behavioral responses akin to IOR? 2) Can we find neural correlates of IOR in the responses of the barn owl's OT? Owls rely both on visual and auditory inputs for rapid detection of small prey items in highly cluttered, dimmed and noisy environments, conditions that are challenging to any attentional system. Barn owls (Tyto alba) have been shown to possess well-developed bottom-up attentional mechanisms, including cueing effects, attentional capture and pop-out perception 22-24. Moreover, the OT of barn owls has been studied thoroughly, providing a system that is well characterized and accessible for electrophysiological analysis 25,26. To facilitate comparison, we tested two barn owls in a Posner cueing task commonly used in humans and monkeys 27,28. Although the two owls showed behavioral differences, the responses were comparable to the results measured from human subjects, suggesting the existence of basic IOR in barn owls. In a parallel experiment, we measured neural responses in the OT of owls, passively viewing a cueing paradigm as in the behavioral experiments. Neural responses were stronger for the validly cued targets at short time lags and stronger for the invalidly cued targets at longer time lags. These results support the notion that IOR is a basic mechanism in the evolution of vertebrate behavior and suggest that the effect appears as a result of the interaction between lateral and forward inhibition in tectal circuitry. Methods Animals. Six adult barn owls were used in this study. The owls were hatched and raised in captivity and housed in aviaries equipped with perching spots and brooding boxes. All procedures were in accordance with the guidelines and were approved by the Technion's Institutional Animal Care and Use Committee. All surgical procedures were performed under isoflurane anesthesia, and the animals were sedated with a mixture of oxygen and nitrous oxide in all recording sessions. No painful procedures were carried out during the recording sessions.

The elucidation of spatial coding in the hippocampus requires exploring diverse animal species. While robust place-cells are found in the mammalian hippocampus, much less is known about spatial coding in the hippocampus of birds - and nothing is known about avian spatial representation during flight. Here we used a wireless-electrophysiology system to record single neurons in the hippocampus and related pallial structures from freely flying barn owls (Tyto alba) - a central-place nocturnal predator species with excellent navigational abilities. The owl 3D position was monitored while it flew back and forth between two perches. We found place cells - neurons that robustly represented the owls location during flight, and its flight-direction - as well as neurons that coded the owls perching position between flights. Spatial coding was invariant to changes in lighting conditions and to the position of a salient object in the room. Place cells were found in the anterior hippocampus and in the adjacent posterior hyperpallium apicale, and to a much lesser extent in the visual Wulst (visual-cortex homologue). The finding of place-cells in flying owls suggests commonalities in spatial coding across a variety of species - including rodents, bats and owls.

The elucidation of spatial coding in the hippocampus requires exploring diverse animal species. While robust place-cells are found in the mammalian hippocampus, much less is known about spatial coding in the hippocampus of birds. Here we used a wireless-electrophysiology system to record single neurons in the hippocampus and other two dorsal pallial structures from freely flying barn owls ( Tyto alba ), a central-place nocturnal predator species with excellent navigational abilities. The owl’s 3D position was monitored while it flew between perches. We found place cells—neurons that fired when the owl flew through a spatially restricted region in at least one direction—as well as neurons that encoded the direction of flight, and neurons that represented the owl’s perching position between flights. Many neurons encoded combinations of position, direction, and perching. Spatial coding was maintained stable and invariant to lighting conditions. Place cells were observed in owls performing two different types of flying tasks, highlighting the generality of the result. Place coding was found in the anterior hippocampus and in the posterior part of the hyperpallium apicale, and to a lesser extent in the visual Wulst. The finding of place-cells in flying owls suggests commonalities in spatial coding across mammals and birds.