Vision and visual navigation in nocturnal animals The most basic research into how nocturnal animals see well in very dim light has led to surprising applications in digital imaging techology. We spoke to Professor Eric Warrant about his work exploring how insects and other animals see in the dark “Most people think of insects as lower life-forms, but they’re not. They are really sophisticated and have amazing brains. The brain of an insect is divided into many sub-regions. There’s a whole area devoted entirely to vision, and this visual area alone is broken down into even more sub-structures, each of which has hundreds of thousands of neurons connected in every possible combination.”
number of questions about how exactly their visual systems work. It is this quest for discovery which has driven Professor Warrant’s work. The project itself has a four pronged approach to the study. In order to investigate just how well insects can see, and testing the extent of their visual performance, Professor Warrant will be carrying out behavioural studies. In
Professor Eric Warrant has had an active interest in the study of nocturnal insects for many years; his research stems from a desire to discover how nocturnal insects see so well in an environment where there is very little light. “Nocturnal insects can see a lot better than we can,” Professor Warrant says, “and my research is not just about trying to determine the kind of visual power these insects have in dim light, but also trying to work out exactly how it is that they see so well.” The Seeing in the Dark project is not just looking at the physical properties of insect eyes, but is taking a closer look at the neural processes that occur within the brains of the insects as they navigate in dim light. “I wanted to find out what special tricks these creatures have,” says Professor Warrant. “How can they see colour? How are they able to fly through a dark forest at night without crashing into trees? How do they learn visual landmarks and recall them to find their homes in what can be a visually complicated environment, where we ourselves would have great difficulties finding our way in bright light?” When we consider the relative size of an insect, and therefore the size of their eyes and brains, the fact that they have such sophisticated optical abilities poses a
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recent studies, he and his colleagues have shown that it is possible to train a nocturnal hawk moth to associate the colour blue with food; from this, it is then possible to introduce further stimuli, such as striped patterns or different shapes, to test spatial resolution. “What we have learned from this,” Professor Warrant says, “is that they can see colours at night, whereas we and nearly all other vertebrates cannot.” Some insects have the innate ability to see very faint patterns of polarised light, which are produced around the moon; it is this
ability which allows them to navigate in the dark. The second approach is to study the neural performance of the insects with electrophysiology, using electrodes to investigate specific neurons that have been identified in the visual system. “Traditionally, we have been working mainly in the retina,” says Professor Warrant. “We have been recording from photoreceptors and looking at what specific properties of the photoreceptors suit them for life in very dim light.” Following this, the aim is to look further into the brain and investigate different circuits of neurons; the hope is to discover how these circuits improve and enhance the visual signal as it passes from the retina to the brain. “Its not a trivial task at all to get to the bottom of this, but the higher you get in the visual system in terms of finding circuits of cells within the brain that deal with vision, the more you can learn. The hope is that we can build a picture of the strategies that these insects use neurally. I would hope that within five to ten years, we will be able to do this, but whether we can actually pin down the exact circuitry and know which cells are involved and how they are connected and exactly what they do, I will be very pleased if we can do that before I retire.” Thirdly is the study of the eye itself, looking at the optics and structure of the eye. “We are trying to work out exactly how sensitive to light the optics and morphology of the eye are and determining what exactly this adds to the nocturnal visual system,” Professor Warrant says. The fourth approach is to compile a theoretical understanding of the insect nocturnal visual system, based upon the
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At a glance information gathered in the preceding three stages. Using behavioural, physiological, optical and anatomical results, Professor Warrant hopes to build up a complete picture of the insects’ visual system and use that knowledge to create models of nocturnal vision and visual performance. “From our previous studies on what’s going on at the level of neurons, and what’s going on at the level of behaviour, we see that there is a huge gap,” Professor Warrant says. “So far, we haven’t really nailed the exact mechanisms that the brain is using for allowing nocturnal animals to see so well in very dim light. Their behaviour vastly exceeds their apparent visual abilities at the level, at least, of the photoreceptors. This is about animals doing things which are seemingly impossible.”
algorithm,” Professor Warrant says. “It’s like an eye really; it works in the same way.” As a result of the development of the algorithm, Professor Warrant is one of the founders of a start-up company to promote the software. Nocturnal Vision AB, based in Sweden, have demonstrated the effectiveness of the algorithm and posted several videos on their website showcasing the images created by it. The possible applications for the algorithm are quite numerous. “It could be developed for use in consumer cameras for improving filming at night, one could have them in mobile phones, or for any other application that requires cameras and video, such as surveillance, military use, and microscopes among others,” Professor Warrant says.
While the Seeing in the Dark project is concerned with investigating the properties of nocturnal insects’ eyes, there is a lot more to the project than meets the eye. During the course of his research, Professor Warrant and his colleagues have developed an algorithm that could be developed commercially with a number of applications. “For me, the development of this algorithm was wonderful,” he says. “It was the result of pure blue-skies, curiosity driven research.”
Several years ago, car manufacturer Toyota approached Professor Warrant to offer their assistance in helping to develop the algorithm; they provided funding for five years and employed two mathematicians to help with the project. The hope is to create a colour camera that could assist with driving during the night.
The algorithm takes some of the principles that Professor Warrant has discovered in his investigation of nocturnal insects and applies them to digital images captured in very dim light, or by cameras which have very small lenses that cannot capture all of the available light. It works dynamically to enhance the colours captured in the image, providing an image which is strikingly clear. “The advantage of the algorithm is that you don’t require another light source,” explains Professor Warrant. “For example, with most night-vision goggles, you illuminate the world with infra red light; this technique is based on the way animals see, and they don’t have lamps built into their heads. They’re trying to work with existing light levels, so the philosophy of the algorithm is to do the same; to adapt to light levels as an insects’ visual system would.” As existing light levels grow dimmer, the algorithm works harder, and it is able to monitor light levels itself; therefore when light levels change again, it can either work harder or turn itself off. “It is a clever
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It is difficult to imagine that the nocturnal visual abilities of insects could have such a potential impact on our everyday consumer lives. For Professor Warrant, the varied range of the project is what makes it so refreshing. “It’s a wonderful project because there’s a lot of lab work, and a lot of field work. You could find yourself in Panama, where we’ve been studying nocturnal bees, or South Africa, where we’re working on dung beetle navigation at night. We’ve even had a project in India studying a giant nocturnal bee; it’s about 4cm long and stings like a sidewinder missile. It’s not very often that bees become nocturnal, but in hot areas of the world, particularly tropical and hot arid areas, there is so much competition during the day for limited flower resources, and so many predators, that these bees have drifted into the night. What makes this bee in India so remarkable is that it has taken its daylight eyes with it; the optical design of their eyes is best suited to bright daylight, but they’re seeing incredibly well at night, which makes the demand on the neural circuitry even greater. This has really fascinated us. I just hope that one day we can solve the mystery.”
Full Project Title Seeing in the dark: Vision and visual behaviour in nocturnal and deep-sea animals. Project Objectives The objective of the project is to determine the optical and neural strategies used by nocturnal and deep-sea animals to see well in very dim light Project Funding The Swedish Research Council (VR) (2010-2012): 700,000 SEK per year The US Air Force Office of Scientific Research (2009-2011): 750,000 SEK. Contact Details Project Coordinator, Professor Eric Warrant Department of Biology University of Lund Sölvegatan 35 S-22362 Lund Sweden T: +46 46 2229341 F: +46 46 2224425 E: eric.warrant@biol.lu.se W: www.lu.se/o.o.i.s/8213
Professor Eric Warrant
Project Coordinator
Eric Warrant is Professor of Zoology and Director of Postgraduate Studies in Biology at the University of Lund, Sweden. He is a Fellow of the Royal Danish Academy of Sciences and Letters, the Royal Physiographic Society of Lund, and Vice Chairman of the National Committee for Biology (Royal Swedish Academy of Sciences). His collaborations with Toyota to develop night vision systems for cars resulted in the forming of a new company, Nocturnal Vision AB, of which he is part owner.
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