Vibrio cholerae is the cause of cholera, a devastating epidemic and pandemic disease. Despite its importance, the way of its global dissemination is unknown. V. cholerae is abundant in aquatic habitats and is known to be borne by copepods, chironomids and fishes. Our aim was to determine if fish-eating birds act as vectors in the spread of V. cholerae by consuming infected fish. We determined the existence of V. cholerae in the microbiome of 5/7 wild cormorants’ intestine. In three of these V. cholerae-positive wild cormorants, the presence of a gene for cholera toxin (ctxA) was detected. We subsequently tested eight captive, hand-reared cormorants, divided into two equal groups. Prior to the experiment, the feces of the cormorants were V. cholerae-negative. One group was fed exclusively on tilapias, which are naturally infected with V. cholerae, and the other was fed exclusively on goldfish or on koi that were V. cholerae-negative. We detected V. cholerae in the feces of the tilapia-fed, but not in the goldfish/koi-fed, cormorants. Hence, we demonstrate that fish-eating birds can be infected with V. cholerae from their fish prey. The large-scale movements of many fish-eating birds provide a potential mechanism for the global distribution of V. cholerae.

Understanding brain function requires repeatable measurements of neural activity across multiple scales and multiple brain areas. In mice, large scale cortical neural activity evokes hemodynamic changes readily observable with intrinsic signal imaging (ISI). Pairing ISI with visual stimulation allows identification of primary visual cortex (V1) and higher visual areas (HVAs), typically through cranial windows that thin or remove the skull. These procedures can diminish long-term mechanical and physiological stability required for delicate electrophysiological measurements made weeks to months after imaging (e.g., in subjects undergoing behavioral training). Here, we optimized and directly validated an intact skull ISI system in mice. We first assessed how imaging quality and duration affect reliability of retinotopic maps in V1 and HVAs. We then verified ISI map retinotopy in V1 and HVAs with targeted, multi-site electrophysiology several weeks after imaging. Reliable ISI maps of V1 and multiple HVAs emerged with ~ 60 trials of imaging (65 ± 6 min), and these showed strong correlation to local field potential (LFP) retinotopy in superficial cortical layers (r2 = 0.74–0.82). This system is thus well-suited for targeted, multi-area electrophysiology weeks to months after imaging. We provide detailed instructions and code for other researchers to implement this system.

Perceiving an object as salient from its surround often requires a preceding process of grouping the object and background elements as perceptual wholes. In humans, motion homogeneity provides a strong cue for grouping, yet it is unknown to what extent this occurs in nonprimate species. To explore this question, we studied the effects of visual motion homogeneity in barn owls of both genders, at the behavioral as well as the neural level. Our data show that the coherency of the background motion modulates the perceived saliency of the target object. An object moving in an odd direction relative to other objects attracted more attention when the other objects moved homogeneously compared with when moved in a variety of directions. A possible neural correlate of this effect may arise in the population activity of the intermediate/deep layers of the optic tectum. In these layers, the neural responses to a moving element in the receptive field were suppressed when additional elements moved in the surround. However, when the surrounding elements all moved in one direction (homogeneously moving), they induced less suppression of the response compared with nonhomogeneously moving elements. Moreover, neural responses were more sensitive to the homogeneity of the background motion than to motion-direction contrasts between the receptive field and the surround. The findings suggest similar principles of saliency-by-motion in an avian species as in humans and show a locus in the optic tectum where the underlying neural circuitry may exist. A critical task of the visual system is to arrange incoming visual information to a meaningful scene of objects and background. In humans, elements that move homogeneously are grouped perceptually to form a categorical whole object. We discovered a similar principle in the barn owl's visual system, whereby the homogeneity of the motion of elements in the scene allows perceptually distinguishing an object from its surround. The novel findings of these visual effects in an avian species, which lacks neocortical structure, suggest that our basic visual perception shares more universal principles across species than presently thought, and shed light on possible brain mechanisms for perceptual grouping.

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.