| 1. |
- Baird, Emily, et al.
(författare)
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A universal strategy for visually guided landing.
- 2013
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Ingår i: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 110:46, s. 18686-18691
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Tidskriftsartikel (refereegranskat)abstract
- Landing is a challenging aspect of flight because, to land safely, speed must be decreased to a value close to zero at touchdown. The mechanisms by which animals achieve this remain unclear. When landing on horizontal surfaces, honey bees control their speed by holding constant the rate of front-to-back image motion (optic flow) generated by the surface as they reduce altitude. As inclination increases, however, this simple pattern of optic flow becomes increasingly complex. How do honey bees control speed when landing on surfaces that have different orientations? To answer this, we analyze the trajectories of honey bees landing on a vertical surface that produces various patterns of motion. We find that landing honey bees control their speed by holding the rate of expansion of the image constant. We then test and confirm this hypothesis rigorously by analyzing landings when the apparent rate of expansion generated by the surface is manipulated artificially. This strategy ensures that speed is reduced, gradually and automatically, as the surface is approached. We then develop a mathematical model of this strategy and show that it can effectively be used to guide smooth landings on surfaces of any orientation, including horizontal surfaces. This biological strategy for guiding landings does not require knowledge about either the distance to the surface or the speed at which it is approached. The simplicity and generality of this landing strategy suggests that it is likely to be exploited by other flying animals and makes it ideal for implementation in the guidance systems of flying robots.
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| 2. |
- Malm, Henrik, et al.
(författare)
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Biologically inspired enhancement of dim light video
- 2012
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Ingår i: Frontiers in Sensing: From Biology to Engineering. - Vienna : Springer Vienna. - 9783211997499 - 9783211997482 ; , s. 71-85
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Bokkapitel (refereegranskat)abstract
- In this chapter a technology for the enhancement of video data obtained at low light levels is presented. The method was inspired by the way in which nocturnal animals adaptively sum intensities, spatially and temporally, to improve vision at night. Due to the low photon count under these conditions the visual input is dark and unreliable, which leads to noisy low contrast images. The noise becomes very apparent when we try to enhance the contrast and, by this, amplify the intensities in the darkest regions of the images. By constructing spatio-temporal smoothing kernels that automatically adapt to the three dimensional intensity structure at every point, the noise can be considerably reduced, with fine spatial detail being preserved and enhanced without added motion blur. For color image data, the chromaticity is restored and demosaicing of raw RGB input data can be performed simultaneously with the noise reduction. The method is a very generally applicable one, contains only few user-defined parameters and has been developed for efficient parallel computation using a graphics processing unit (GPU). The technique has been applied to image sequences with various degrees of darkness and noise levels. Results from some of these tests, and comparisons to related work, are presented here.
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| 3. |
- Moore, Richard JD, et al.
(författare)
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FicTrac: A visual method for tracking spherical motion and generating fictive animal paths
- 2014
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Ingår i: Journal of Neuroscience Methods. - : Elsevier BV. - 1872-678X .- 0165-0270. ; 225, s. 106-119
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Tidskriftsartikel (refereegranskat)abstract
- Studying how animals interface with a virtual reality can further our understanding of how attention, learning and memory, sensory processing, and navigation are handled by the brain, at both the neurophysiological and behavioural levels. To this end, we have developed a novel vision-based tracking system, FicTrac (Fictive path Tracking software), for estimating the path an animal makes whilst rotating an air-supported sphere using only input from a standard camera and computer vision techniques. We have found that the accuracy and robustness of FicTrac outperforms a low-cost implementation of a standard optical mouse-based approach for generating fictive paths. FicTrac is simple to implement for a wide variety of experimental configurations and, importantly, is fast to execute, enabling real-time sensory feedback for behaving animals. We have used FicTrac to record the behaviour of tethered honeybees, Apis mellifera, whilst presenting visual stimuli in both open-loop and closed-loop experimental paradigms. We found that FicTrac could accurately register the fictive paths of bees as they walked towards bright green vertical bars presented on an LED arena. Using FicTrac, we have demonstrated closed-loop visual fixation in both the honeybee and the fruit fly, Drosophila melanogaster, establishing the flexibility of this system. FicTrac provides the experimenter with a simple yet adaptable system that can be combined with electrophysiological recording techniques to study the neural mechanisms of behaviour in a variety of organisms, including walking vertebrates
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| 4. |
- Paulk, Angelique C, et al.
(författare)
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Selective attention in the honeybee optic lobes precedes behavioral choices
- 2014
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Ingår i: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 111:13, s. 5006-5011
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Tidskriftsartikel (refereegranskat)abstract
- Attention allows animals to respond selectively to competing stimuli, enabling some stimuli to evoke a behavioral response while others are ignored. How the brain does this remains mysterious, although it is increasingly evident that even animals with the smallest brains display this capacity. For example, insects respond selectively to salient visual stimuli, but it is unknown where such selectivity occurs in the insect brain, or whether neural correlates of attention might predict the visual choices made by an insect. Here, we investigate neural correlates of visual attention in behaving honeybees (Apis mellifera). Using a closed-loop paradigm that allows tethered, walking bees to actively control visual objects in a virtual reality arena, we show that behavioral fixation increases neuronal responses to flickering, frequency-tagged stimuli. Attention-like effects were reduced in the optic lobes during replay of the same visual sequences, when bees were not able to control the visual displays. When bees were presented with competing frequency-tagged visual stimuli, selectivity in the medulla (an optic ganglion) preceded behavioral selection of a stimulus, suggesting that modulation of early visual processing centers precedes eventual behavioral choices made by these insects.
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| 5. |
- Taylor, Gavin, et al.
(författare)
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Vision and air flow combine to streamline flying honeybees
- 2013
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 3:Article Number: 2614
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Tidskriftsartikel (refereegranskat)abstract
- Insects face the challenge of integrating multi-sensory information to control their flight. Here we study a 'streamlining' response in honeybees, whereby honeybees raise their abdomen to reduce drag. We find that this response, which was recently reported to be mediated by optic flow, is also strongly modulated by the presence of air flow simulating a head wind. The Johnston's organs in the antennae were found to play a role in the measurement of the air speed that is used to control the streamlining response. The response to a combination of visual motion and wind is complex and can be explained by a model that incorporates a non-linear combination of the two stimuli. The use of visual and mechanosensory cues increases the strength of the streamlining response when the stimuli are present concurrently. We propose this multisensory integration will make the response more robust to transient disturbances in either modality.
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